To explore the function of the active components of Polygonum hydropiper and expand the application scene of P. hydropiper,the volatiles of P. hydropiper were extracted by water extraction and alcohol extraction respectively, and the components of the extracts were identified by gas chromatography-mass spectrometry (GC-MS), the biological activity of the P. hydropiper extracts was explored by bacteriostatic test and inhibition of growth and survival of Helicoverpa armigera.The results show that: the alcohol extract of P. hydropiper were identified 16 picks in the volatile oil of P. hydropiper isolated, among them, four compounds were identified,the water extract of P. hydropiper were identified 15 picks in the volatile oil of P. hydropiper isolated, among them, three compounds were identified;the extract of P. hydropiper had certain bacteriostatic effect and had certain restraining influence on the biological activity of H. armigera.The results suggest that: the effect of 95% ethanol in extracting the volatile compounds of P. hydropiper is better than that of water, and the biological activity of the volatile substances of P. hydropiper needs to be further verified.