Abstract: A study on the adaptation of Calanus sinicus to environment factors was carried out to explore the distribution and the response of Calanus sinicus affected by the changing environmental factors in different waters of the South Yellow Sea and East China Sea in spring 2020. The generalized additive models were used to analysis the density changes of C. sinicus with the environmental factors. Results showed that C. sinicus was the dominant species in the survey area. The densities of C. sinicus in coastal waters from Haizhou Bay to Changjiang Estuary variated with temperatures with the lowest density at 14 ℃. The densities of C. sinicus varied with increasing chemical oxygen demand. It dropped down at first and then increased with increasing chlorophyll-a concentration. In addition, the densities of C. sinicus varied with increasing dissolved oxygen and reached the lowest at 10 mg/L. The densities reduced with the increasing pH and increased with the concentration of ammonia nitrogen rising. In Changjiang Estuary, the densities increased with the increasing water depth and salinity, decreased with rising chemical oxygen demand and active phosphate concentration. In waters of Sanmen Bay, it increased with increasing salinity, decreased with rising pH, decreased first then increased at the transparency of 1.2 meter. In the central Fujian coastal waters, the densities of C. sinicus increased with the increasing water depth, decreased with increasing temperature and dissolved oxygen and it fluctuated with increasing transparency.