Abstract: In order to analyze the chemical constituents of the extracts of Polygonum hydropiper L. with different mesh numbers. The chemical constituents of Polygonum hydropiper L. with different numbers were analyzed by time of flight mass spectrometry with super-high-performance liquid chromatography pole(UPLC-Q-TOF/Ms). The volume size of Polygonum hydropiper L. powder with different mesh decreased with the increase of mesh number;the average area size decreased from 50 mesh to 300 mesh,and then increased gradually;the surface of powder particles became more and more smooth with the increase of mesh number,and the characteristics of original medicinal materials became less and less obvious.17 compounds were isolated and identified from different mesh powder extracts,including 9 flavonoids,5 phenylpropanoids,1 organic acid,polysaccharide and tannin respectively,among which Vanicoside C was not detected in 200 mesh and 300 mesh powder;the peak area value of flavonoids gradually increased from the powder passing through the 50 mesh sieve,a higher peak area value appeared at 120 mesh,then gradually decreased from 200 to 300 mesh,and gradually increased to 500 mesh. Among them,the relative peak area value of quercetin was 47.11%;the peak area value of phenylpropanoid compounds dropped from 50 mesh to the lowest value of 300 mesh,and then showed an upward trend,of which Vanicoside B relative peak area value was 47.79%. It provides an important basis for clarifying the action mechanism of active chemical components and the basis of effective substances.