Abstract: Compost is one of the disposal ways for the municipal solid wastes (MSW). During the MSW compost, nitrogen forms are different owing to the different compost materials. So far, there have been few reports on the changes of (organic) nitrogen forms. This paper dealt with changes of organic nitrogen forms during composting with municipal solid wastes. Two-step fermentation was adopted in experiment where two types of microbes were inoculated during composting with MSW. The process indices were designed according to those of the industrialized compost. At different compost phases, the samples were taken for the determination of the nitrogen forms. The results showed the total nitrogen and acid hydrolyzing nitrogen content obviously decreased during the composting, and were lower in the treatment with microbe (inoculation) than in that without inoculation at different periods of composting, but there were no obvious differences at (the) end of composting. The content of amino acid nitrogen increased at the primary period, then decreased at the decomposed period of composting. At the end of composting, it increased significantly compared with of the treatment without inoculation. These results showed that inoculation with microbes would be beneficial for the formation of amino acid nitrogen. The contents of amide nitrogen and amino sugar nitrogen increased at the periods of temperature rising and high temperature, and decreased as temperature declined, then were constant at the decomposed period. But at the different periods of composting, the contents of amide nitrogen and amino sugar nitrogen were obviously different among the different treatments. The contents of amide nitrogen in the treatment with inoculation of microbes were obviously increased compared with of the treatment without inoculation, while the reverse was true for amino sugar nitrogen. It can be concluded that inoculation with microbes in compost could accelerate the mineralization of organic nitrogen, and the ratio of C/N could not be used as an index for evaluation of compost maturity.