Abstract: The growth rate and the nutrient composition of Chaetoceros gracilis cells， as one of important food organisms for breeding marine commercial animals， significantly affect the breeding efficiency and the quality of aquaculture larvae. The effects of three factors， including temperature， salinity and ultrasonic wave， on growth， protein and lipid contents of C. gracilis were studied in respective single factor experiments. The results indicate that temperature and salinity significantly affected the growth of C. gracilis while the 5～40 min treatments with ultrasonic wave did not have significant difference in growth. The optimal conditions for C. gracilis growth are at temperature 25 ℃ and salinity 25. The protein and lipid contents of C. gracilis were significantly affected by all three factors， among which ultrasonic wave treatment bought the highest difference. The short time （5 min） ultrasonic wave treatment resulted in highest protein content and long time （40 min） ultrasonic wave treatment led to the highest lipid content in C. gracilis cells. The experimental results in present study provided an important reference basis for designing treatment in the second stage of twostage culture for microalgae.