This study focused on the nitrogen (N) and phosphorus (P) removal characteristics in simultaneous nitrification-endogenous denitrification and phosphorus removal (SNEDPR) system treating low carbon/nitrogen (C/N) ratio (<3) wastewater. In order to achieve an efficient nutrient removal, an extended anaerobic/low aerobic (dissolved oxygen:0.5~1.0mg/L) sequencing batch reactor (SBR) fed with municipal sewage was started up and optimized by regulating the influent C/N ratio. The population dynamics of functional microorganisms were also analyzed. Results indicated that when the influent C/N ratio raised from 4.3 to 5.15, the N and P removal performance of the system became better with total nitrogen (TN) and PO₄^3--P removal efficiencies up to 89.3% and 90.6%, respectively; with C/N ratio reduced to <3, the nutrient removal performance decreased firstly and then increased in the following operation. However, the effect of low C/N on the phosphorus removal performance of PAOs (phosphorous accumulating organisms) was higher than the endogenous denitrification capability of DGAOs (denitrifying glycogen accumulating organisms), showed as the TN and PO₄^3--P removal efficiency reduced to 21.4% and 3.4% firstly, and lately increased to 92.9% and 94.1% gradually. In the stable phase of the system, the average phosphorus release per COD and SNED efficiency reached to 437.1mg/L and 89.1% respectively, with the average effluent concentration of NH₄⁺-N, NO_x^--N and PO₄^3--P was 0, 4.4, and 0.2mg/L, respectively. After 136-day operation, PAOs, GAO, AOB (ammonia oxidizing bacteria) and NOB(nitrite oxidizing bacteria) accounted for 16%±3%, 8%±3%, 7%±3% and 3%±1% of total biomass, respectively, which ensured the P uptake, nitrification and denitrification. Additionally, the occurrence of simultaneous partial nitrification-endogenous denitrification at the low aerobic stage of the system interpreted the efficient nutrient removal from low C/N (<3) wastewater.