Hemp thread is the algae of chordates in Chordata Family, and it is rich in nutrition. If stored in the refrigerator, it can effectively inhibit the growth of bacteria, thus increasing the storage time of hemp thread.

Hemp thread is rope algae, also known as hemp rope vegetables and sea gazi, which is named after it looks like a rope. It grows on underwater rocks and is distributed along the coast of the Yellow Sea and Bohai Sea in China. The algae body is grayish black to dark brown, slender, rope-shaped, with a diameter of 1.5-3.0cm, single unbranched, narrow at both ends, hollow at the upper part and solid at the lower part. The hollow part is divided into many cavities by the diaphragm.