The bait that the adult Dalian purple sea urchin feeds on in the natural sea area includes a variety of macroalgae, benthic diatoms, some small shellfish and organic debris, etc., of which kelp, Ulva schreberi and other algae are the main ones. The results also showed that the bait consumed by adult sea urchins is related to the bait organisms in the waters where they live. When the bait organisms are abundant, the adult sea urchins are selective in feeding on the bait. For the three major types of seaweeds, namely green algae, red algae and brown algae, the selectivity was in the order of brown algae, red algae and green algae. Among the brown algae, the brown algae were most addicted to wakame, kelp, etc.; among the red algae, the red algae were addicted to angiosperm algae and rockweed; among the green algae, the green algae were addicted to Ulva schreberi and seaweed. For some animal bait, such as fish and shellfish meat, adult sea urchins also have good feeding habits. Thus, the feeding habits of adult sea urchins should be omnivorous.