Abstract: To study the spatial distribution and environmental adaptability of Acaudina molpadioides in Western Daya Bay, we carried out field investigation in January, March, August and November, 2020, respectively. The living habits ofA. molpadioideswere analyzed based on the breeding experiment and sediment characteristics. The results indicated that (1) the biomass of A. molpadioides reached 170 g/m² in clay-silt and more A. molpadioides were found in the low temperature seasons. (2) According to the PCA analysis, we found that A. molpadioidestends to be present in the clay-silt environment where the water depth, salinity and dissolved oxygen were higher, and the water temperature and Chl.a content were lower. (3) We found that A. molpadioides lives in the sediments upside-down feeding on the black clay beneath the clayey silt layer. (4) There was no significant tubular foot on the body surface, and there was only fifteen tentacles around its mouth. Therefore,A. molpadioides had poor adhesive ability. (5) According to the PCA analysis, we found that A. molpadioides tends to live in the clay-silt and sandy silt environments where temperature was lower and salinity was higher, comparatively. The numbers of collected A. molpadioides were higher in winter, spring and summer than that in autumn, and its life history needs to be studied further.