As one of the three main projects of the Dujiangyan Water Conservancy Project, the fish's mouth, its role is to divide the water of the Minjiang River into two, so that it plays a diversion of water, flood drainage and sand discharge. The word "fish mouth" for the Ming Dynasty since the term, the first in the text is the Ming Jiaqing GaoShao made "Dujiangyan iron cattle record monument": "Where the iron sixty-seven thousand kilograms of iron and into two cattle, standing weir mouth of the middle flow, when the two rivers surging momentum. Complex set up three iron pile in the cattle under the stream, to solid fish mouth of the stone, mouth as usual, still set the bamboo cage bamboo volume to protect the river to solid, all the weir with", here appears "fish mouth" seems to refer to the front of the current King Kong embankment, after the "fish mouth" The name has been used. To modern times, "the mouth of the fish" really refers to the front of the dike, such as: "irrigation county Dujiangyan Water Conservancy Zhi" in the introduction of the project and the project location illustration will also be the front of the dike known as the mouth of the fish. I thought that the "fish mouth" of the specific reference may be a misunderstanding, the reason why the ancients to "fish mouth" for the water diversion project name, I thought with the real mouth of the fish is closely related. As long as a little attention is not difficult to observe, fish in the water to gill breathing, water from the mouth and by the two gills out, this into a water into two, which is not with the mouth of the fish project "diversion of water" of the work in line with it? From the fish mouth breathing principle, inside and outside the river centerline intersection to the end of the river above both sides of the Jin Gang embankment this water project is not precisely a section of the Minjiang River built into a large fish mouth? It makes the entire Minjiang River water from the mouth of the fish swallowed, and then spit out by the two gills, the left gill flow into an external river, the right gill flow into the inner river, the center line of the mouth of the fish pointing to the Minjiang River at the bend in the right bank, so that the left gill center line aligned with the center of the river, the flood, the main stream injected into the left gill into the Jinma River, draining away a large number of floods, sand and gravel; the mouth of the whole horizontal position tilted to the right side, the dry season, river through the right gill can try to flow into the river. Play a "four six, flat drought and drought" role, the head of the canal downstream and then by the Neijiang through the size of the second and third level of the fish mouth, the formation of tributaries densely populated irrigation network, watering the wilderness of Tianfu. Ancient people in the first for the water diversion project name, must have gotten the fish mouth of the revelation, just due to various reasons will be it for the misrepresentation. King Kong embankment front as a key project into the water project is deserved, but it will be regarded as "fish mouth", I think it is inappropriate. The front end of the dike as the mouth of the fish is also the dike as a fish, the dike in the river, from the appearance of the dike, the shape of the fish, but the fish in the water can only swim and does not have the function of the water, because the fish is small compared with the swimming water. If the front end of the dike is both the key to share water and the most easily damaged part of the overall project as a "fish mouth" theory, I think it is understandable, but as a project, we not only want to recognize it from its appearance, but also from the function of understanding, and in practice we have long been the "fish mouth" as one of the three major Dujiangyan projects, the "fish mouth" as one of the three major Dujiangyan projects. "As one of the three major components of Dujiangyan, it is known as the water diversion project. The diamond embankment and its front end are only the key facilities of this project, if there is no complete outer diamond embankment and the proper cooperation of the water flow bends and other factors, it is difficult to realize the function of water diversion satisfactorily, if only the key part is treated as a whole, it is just like the white part of the cloth in the painting that is not counted by the painting when we are looking at a painting of a landscape. Correct understanding of the fish mouth, we recognize the Dujiangdu water diversion project has important significance.