Through the measure of tannin and phenol constituents of 6 poplars,the relation between the resistance of poplars and contents and components of them was studied. The results showed that: the contents of tannin in xylem is positively related to the resistance of poplars,but those in phloem have nothing to do with the resistance . The resistance of poplars is higher with higher contents of phenol constituents,and there is a different trend with the different phenol.