This work describes the variations in nitrogen (N) and phosphorus (P) removal performances and bacterial population dynamics in response to different influent C/N and C/P ratios in a novel BNR-IC process combining biological nutrients removal (BNR) with induced crystallization (IC). A good nutrients removal performance was achieved at 7.8 of C/N ratio and 23.3 of C/P ratio, where P and TN removal efficiencies were 94.0±2.4% and 90.5±4.3%, respectively. Moreover, significant changes of microbial community structure were found with the variations of influent C/N and C/P ratios. Increasing influent C/N and C/P ratios favored the development of DPAO, thus enhancing the TN and P removal efficiencies and causing a decrease in microbial community biodiversity. However, excessive P load in the influent strongly influenced the P removal performance when C/N
ratio was maintained at appropriate levels. PCR-DGGE showed that microbial populations in sampled sludge were classified into five different phylum or class (Alpha-, Beta-, and Gammaproteobacteria, as well as Firmicutes, Actinobacteria).