Preliminary study on the active component of Radix peucedani capable of inducing rice resistance to blast was carried out by tracing bioassay. The acetone extract showed better inducive effect on the resistance to rice blast disease(Magnaporthe grisea) compared to other solvent extracts. The acetone extract was isolated by silica gel column chromatography. The fractions A4, A5, A6 were more active than others.The effects of inducing resistance of the three fractions at different concentrations were 21.48%～59.54%, and in the three tested concentration range of quality,the effects were higher at the lower concentrations.