Abstract: On the basis of stem profile and relative stem form,the four parameter cylinder volume ratio stem profile was put forward.The results of fitting the data of Pinus tabulaeformis and Quercus aliena from Qinling Mountains showed that the P.tabulaeformis with bark and R2≥0.99 amounted for 93%,that without bark amounted for 78%,while Q.aliena with bark and without bark amounted for 79.8% and 73.3%.This result proved that four-parameter cylinder-volume ratio stem profile has perfect fitness.By estimating the values of four parameters,the graphs of four-parameter cylinder-volume ratio stem profile were established.