Abstract: This study investigated the influence of different factors in maximizing poly--hydroxybutyrate (PHB) accumulation in low-carbon urban sewage. The effects of chemical oxygen demand and total phosphorus (TP) concentrations on PHB accumulation were analyzed using an anaerobic/oxygen sequencing batch reactor. Both the anaerobic phase and the aeration phase were studied. The results showed that maximum PHB accumulations increased as the carbon source increased, growing from 5.45 to 27.51mg/g, when the carbon source concentration increased from 140 to 400mg/L, at the end of anaerobic phase. Maximum PHB accumulation decreased from 15.89 to 13.88mg/g when exposed to influent carbon-phosphorus C/P, suggesting that carbon source is more influential and beneficial for PHB accumulation than TP. With an increase in pre-aeration time from 10 to 50min, PHB accumulation rose from 21.12 to 31.96mg/g; this is higher than 15.54mg/g PHB accumulation without pre-aeration. When the pre-aeration time was fixed at 15min, but with different pre-aeration fluxes ranging from 20 to 50L/h, PHB accumulation increased from 23.79 to 30.09mg/g. These results demonstrate that pre-aeration treatment facilitates PHB accumulation.