Abstract: Compared with that of photoautotrophic cultivation, the characteristics of mixortophic cultivation of Synechocystis sp. PCC 6803 in an enclosed photobioreactor were investigated. The saturated level of light intensity of mixotrophic growth in the photobioreactor was 5 000 lx, which was the same as that of photoautotrophic growth. At incident light intensity 5 000 lx and initial glucose concentration 1.74g/L, after 69.5 h mixotrophic cultivation, 1.36g/L cell density, 20.08mg/L chlorophyll concentration and 16.7% energy efficiency were achieved, which were respectively 3.8 times, 2.3 times and 2.6 times as much as those in photoautotrophic cultivation. On the basis of above results, it was concluded that mixotrophic cultivation system had advantages over photoautotrophic cultivation system for Synechocystis sp. PCC 6803 on production of biomass, photosynthetic pigment and energy utilization.