The effects of coumarins have been studied on seedling rate, stem and leaf dry weight and root dry weight of the tested rice , as well as defense enzymes, soluble protein content, chlorophyll content and proline content with coumarins (peucedanocoumarin Ⅲ, PeucedanocoumarinⅡ, pteryxin) (1,5,10,50,100 mg/L). The coumarin compounds have been used to treat the early rice combination Peiliangyou500 with low temperature stress of(5±1) ℃. The results showed that three coumarin compounds could make seedling rate, stem and leaf dry weight and root dry weight of the tested rice significantly higher than control, and the effect of 50 mg/L was the best. 50 mg∕L coumarin compounds made peroxidase, superoxide dismutase, catalase active and soluble protein content, chlorophyll content. Proline accumulation also increased under low temperature stress.