The aim of this work was to investigate the effects of initial C/N ratio on the total losses of N and C during composting of cattle manure/corn stover mix, and to analyze how the initial C/N ratio impacts the successive progression of the microbiota to affect losses of N and C during the composting. Results indicated that the least of C-loss and N-loss occurred in 35:1 of initial C/N ratio. The succession of predominant bacteria in the composting mix was significantly affected by the temperature and the initial C/N ratio. Redundancy analysis showed that significant negative correlations existed between nitrogen fixing bacteria and N- and C-losses, and significant positive correlations existed between denitrifying bacteria and N- and C-losses. Higher initial C/N ratio appeared to promote growth of nitrogen fixing bacteria while compress the denitrifying bacteria. These results indicated that adjustment of the initial C/N ratio is an important way to control the losses of N and C in the compost. In addition, beneficial nitrogen fixing bacteria could potentially be screened and used as composting supplements to improve the quality of the compost.