Variation of phenolic acids during decomposition of some organic materials was studied by means of moist and aerobic cultivation.The results show that rice straw,pig feces and sawdust contain some kinds of phenolic acids such as p-hydroxybenzoic acid,p-coumaric acid and frulic acid.The contents of p-coumaric acid in rice straw and pig feces are the highest,and followed by that of frulic acid.The content of p-hydroxybenzoic acid in sawdust is the highest,followed by that of p-coumaric acid.During decomposition,the main kinds of phenolic acid in rice straw and pig faces are p-coumaric and frulic acids while in sawdust p-hydroxybenzoic and p-coumaric acids.The total phenolic acid contents are in a decreasing order,rice straw,pig feces,and sawdust.The total phenolic acid contained in the three organic materials reached the maximum after 20~30 days of decomposition,and reached a stable and minimum state after 40~50 days.