The growth status of Chlorella vulgaris, Chlorella proteinosa and Scenedesmus obliquus under different nitrogen levels and the efficiency of advanced nitrogen and phosphorus removal in sewage were compared, and the effect mechanism of nitrogen source level on nitrogen and phosphorus removal in microalgae was analyzed from the perspective of biomacromolecule accumulation. The results showed that the growth of microalgae and the efficiency of nitrogen and phosphorus removal were significantly better than that of the experimental group with ammonia nitrogen as the only nitrogen source, and the content of chlorophyll was also higher than that of the ammonia nitrogen group. The higher the nitrate concentration in each experimental group, the more the number of algae cells, and the growth of chlorella cells was significantly higher than that of Scenedesmus obliquus. Within 7 days, the nitrogen removal rate was above 98% when nitrate concentration ≤8 mg.L-1, but the chlorophyll content was low in the experimental group with low nitrogen concentration. Microalgae by adjusting the content of macromolecular substances in the cell to adapt to different living environment, under the condition of nutrition restricted consumes itself material to meet the needs of life activity, nitrogen conditions can lead to accumulation of lipid in cells, confirmed possibility of nitrogen source level controlling on the depth of the wastewater biological nitrogen and phosphorus coupling feasibility of macromolecular accumulated.