Abstract: To solve poor biological nitrogen removal ability because of low ρ(C)/ρ(N) and insufficient carbon source of sewage wastewater, aerobic/anoxic (O/A) process mode enhancing the accumulation of endogenous organic matter under aerobic condition was explored based on the feast/famine non-steady state theory of activated sludge in this paper. Then, endogenous organic matter was used for denitrification in anoxic condition. When the influent load was 0.31-0.41 g/(g·d) and kept the conditions of 0.11 rate of O/A time, temperature (28±2)℃, sludge retention time(SRT) 20 d, 56.00%±0.09% COD was translated into endogenous polymers and (8.05±1.32)mmol/L endogenous polymers (polyhydroxyalkanoates + glycogen) was successfully accumulated. In the anoxic stage, 40 mg/L NO₃^--N was removed by endogenous polymers and the endogenous denitrification rate was 1.53 mg/1.53 mg/(g·h). Using NO₃^--N or NO₂^--N as electron acceptors, the amount of endogenous polymers for denitrifying nitrogen removal was different and were 2.24 mol endogenous source and 1.59 mol endogenous source, respectively. Endogenous denitrification preferentially consumed PHA, but Glycogen contributed 77% of the denitrifying carbon source. 16S rRNA high throughput sequencing showed that this domestication mode significantly changed the microbial population structure, promoted the abundance of PHA and Glycogen accumulation microbes. Results show that the O/A process can enhance the accumulation of internal carbon sources and enhance the ability of denitrification nitrogen removal.