Based on present serious phenomenon of insufficient carbon source in municipal sewage in China, the two kinds of effect of hybrid-fruit-peel (HFP) coagulant (coagulation and external carbon source (ECS)) on treating low carbon source wastewater was studied, mainly compared with that of sodium acetate (NaAc). The feasibility of HFP as an ECS was researched, and then its coagulation behavior, sludge properties, nitrogen removal were studied mainly with aeration mode and sequencing batch reactor (SBR), respectively. The results showed the ration of biochemical oxygen demand (BOD₅) to chemical oxygen demand (COD) released from HFP was 0.67−0.76, within the scope of easily biodegradable. Within a short aeration time, HFP posed obvious coagulation behavior. HFP sludge gave larger extracellular polymer (EPS) and lower dehydrogenase activity (DHA) than NaAc. For HFP, much larger size sludge flocs appeared, the connection among the flocs became closer, and the biofacies and number of microorganisms (<i>Opercularia Coaractata</i>, <i>Nematode</i>, <i>Vorticella</i>, etc.) increased significantly. HFP can be used as an excellent ECS for low carbon source wastewater, and probably also have the ability of slow-releasing carbon, and can be applied to municipal sewage or other wastewaters with insufficient carbon source.