Abstract: As an excellent resource microalgae, Chlorella has wide applications for aquaculture, production of biofuel and development of functional food, which requires to develop the intensive cultivation pattern and optimize the breeding environment of Chlorella. AHLs(N-acyl-homoserine lactones)are known as the quorum sensing signal molecule produced by commensalism bacteria in phycosphere to regulate the biological function of bacteria and life activities of algae. This study was conducted to evaluate the effects of 100, 200, 300 nmol/LC₁₀-HSL (N-decanoyl-L-homoserine lactones) on PSⅡ photochemistry activity and photosynthesis crucial enzymes of the marine microalgae Chlorella vulga-ris in the photoautotrophic culture process. The results indicated that C₁₀-HSL significantly increased the growth of C. vulgaris by enhanced cell density in dosage-dependent pattern. PSⅡ photochemistry activity indicators—F_v/F_m (maxi-mal photochemical efficiency), Yeild (actual photochemical efficiency) and ETR (apparent photosynthetic electron transport ratio) increased obviously by C₁₀-HSL. C₁₀-HSL had higher effect on Yeild than F_v/F_m. The photosynthesis crucial enzymes—Rubisco (ribulose bisphosphate carboxylase oxygenase), TPI (triose-phosphate isomerase), PFP (pyrophosphate: fructose-6-phosphate-1-phosphoric acid transferase) and FDA (fructose-1,6-bisphosphate aldolase) induced significantly by C₁₀-HSL, indicating enhanced photosynthetic carbon fixation and carbohydrate synthesis.