Abstract: In order to explore the feasibility of microalgal-bacterial granular sludge (MBGS) cultivation from aerobic granular sludge (AGS) and the potential function of key algae species, Chlorella pyrenoidosa (R1 reactor), Chlorella pyrenoidosa and Scenedesmus obliquus (R2 reactor), Chlorella pyrenoidosa, Scenedesmus obliquus, and Leptolyngbya boryana (R3 reactor) were added to the sequencing batch photobioreactor (light intensity of 4 000 lx). The physicochemical characteristics of MBGS, pollutants removal performance and microbial community structure were systematically studied. The results showed that: (1) MBGS could be formed in about 30 days, and the pollutant removal performance under steady state was generally better than that of AGS. The average removal efficiencies of COD, NH₄⁺-N, TN and TP were over 98%, 97%, 77% and 93% for MBGS, respectively, while the NH₄⁺-N and TP removal efficiencies of R2 and R3 reactor were significantly higher than that of R1 reactor (P<0.05). (2) The analysis of extracellular polymeric substances (EPS) showed that R2 and R3 reactor had more aromatic proteins, soluble microbial byproduct, humic acid, fulvic acid, etc. as compared with R1 reactor, which were conducive to the formation of MBGS. (3) Leptolyngbya boryana in R3 reactor was eliminated and the formed MBGS contained the main algae species as R2 reactor. (4) R1, R2 and R3 reactor had more abundant functional microorganisms for nitrogen and such as Nitrospirae and Rhodocyclaceae during the steady state. The study showed that Scenedesmus obliquus might play an important role in the MBGS cultivation by microalgae bio-augmentation, which improved nitrogen and phosphorus removal as well as the MBGS stability.