The study investigated the pollution characteristics of MCR-1and MCR-1hosting bacteria in a municipal wastewater treatment plant in Nanjing, China. Their distribution and influence factors, as well as antibiotic resistance characteristics, were comprehensively assessed. The results indicated that the MCR-1abundance decreased obviously along with the treatment process, with the reduction efficiency of 83.6%. However, its relative abundance increased significantly in the treated effluent. High amount of MCR-1was detected in biosolids, with concentration of up to 2.88×10¹² copies/L. On the other hand, the concentration of colistin resistant bacteria also decreased gradually along with the treatment process. Their concentration decreased to 53 CFU/mL in the final effluent, with the reduction efficiency of 99.98%, but up to 2.04×10⁵ CFU/mL were detected in biosolids. According to the correlation analysis, MCR-1abundance positively correlated with ammonia concentration, while the relative abundance of MCR-1showed negative correlation with COD, TN and NO₃^--N concentration. The antibiotic resistance characteristics analysis indicated that MCR-1hosting bacteria in the activated sludge system (CAST and MSBR) and aeration biological fluid tank (ABFT) were tolerant to significantly higher colistin concentration relative to other sites. Additionally, the level of MCR-1hosting bacteria tolerant to colistin was enhanced by the treatment process, which implied that the wastewater treatment process could not completely reduce MCR-1 and MCR-1hosting bacteria, and even lead to the increase of their potential risks. The study will provide implications for assessing the environmental risks of MCR-1represented super antibiotic resistant genes.