A laboratory study was conducted to investigate the inhibitory components in the rice straw extracts under different degradation manners and time, and their corresponding effects on algae inhibition. It was found that there were algae inhibitory chemicals in rice straw. The inhabitation ratio of rice straw extract to Microcystis was 69.3% when stored at a low temperature of -4℃ for 4 days with a concentration of 2.5g/L. Both anaerobic and aerobic decomposing rice straw extract can be useful for algal inhibition. If stored for 15 days with the concentration of 1.5g/L under anaerobic and aerobic conditions, the inhabitation ratio of rice straw to Microcystis was 83% and 81% respectively. The allelopathic substances were analyzed by using GC-MS, and then the possible mechanism was proposed. The results show that the allelopathic components in the rice straw extracts were mainly naphthylamine, esters and phenols, typically phthalic acid esters (PAEs). The allelppathic components and their concentration in the rice straw extracts decreased along with the straw decomposition time, especially for aerobically decomposed extract. There was a good relationship between the inhibitory effects and the allelppathic components in the rice straw extracts.