Abstract: It was studied of kinds contents and changes of organic acids in the composting of hen feces and dairy manure. The results indicated that there were a lot of organic acids come into being and accumulated; the highest content was 88.2 cmol/kg, DM after 5 weeks of composting; the content of non volatility organic acids has two peaks at the third and fifth week of composting, and the peaks of the volatility acids at the sixth week and ninth week, respectively. After 9 weeks of composting, the content and kinds of organic acids declined sharply. Apart from aromatic acids such as benzoic acid, benzenedicarboxylic acid, etc. and their ramification, there were many small molecular organic acids such as butanedioic acid and its ramification and some big molecular fatty acids come into being. The organic acids in the dairy manure is mainly composed by no volatilization acids, the highest content of acids is 28.38cmol/kg, DM. The main constitutes of no volatilization acids are benzenedicarboxylic acid and its ramifications and big molecule fatty acids. In the composting, there are some hormones detected in the dairy manure.