In this work, different light conditions (light intensity and photoperiodicity) were set up to investigate the impact of light on growth, chemical compositions and fatty acid profiles of Chlorella kessleri in mixotrophic cultures. Results indicated that C. kessleri could absorb and utilize glucose rapidly when light intensity was <= 90 mu E m(-2)S(-1), and a maximum algal biomass of 1.17 g L-1 was obtained in the cultures with 2 g L-1 glucose at a light intensity and light/dark (L/D) cycle of 90 mu E m(-2)S(-1) and 20L:4D, respectively. Additionally, this alga would accumulate a large amount of chlorophyll a (about 30 mg g(-1)) in the mixotrophic cultures under a low light intensity (<90 g m s(-1)), and the algal chemical compositions changed with light intensity and photoperiodicity. Results of fatty acid profiles suggested that the algal biomass could be used as animal feeds or a good -quality biodiesel feedstock.