To obtain efficient denitrifying bacteria with heterotrophic nitrification-aerobic denitrification capacity,a heterotrophic nitrifying-aerobic denitrifying strain with efficient denitrification was screened and isolated from the activated sludge of the southern wastewater treatment plant in Shenyang.A strain named Paracoccussp.QD-30.was identified as Paracoccussp.by 16SrRNA gene sequencing.The studied Paracoccus sp.nitrogen removal characteristics of strain QD-30 under different nitrogen sources and the best nitrogen removal conditions under single environmental factors.The maximum removal rates of ammonia nitrogen,nitrite nitrogen and nitrate nitrogen were 87.69%,77.19% and 77.25%,respectively.The optimum denitrification conditions were as follows:sodium succinate as the best carbon source,C/N of 14,temperature of 35 ℃,pH of 7 and rotational speed of 140 r/min.Paracoccus sp.QD-30 is a new type of paracoccus with high denitrification capacity,which has good engineering application prospects in the field of biological denitrification.