Comparative studies on morphology and structure of the leaf and stem of 10 Euphorbia species were performed using the method of paraffin sectioning and leaf epidermal isolating.The results showed that:(1)The cell morphology of upper and lower epidermis,stomatal size and distribution,and the leaf structure of these 10 species are significantly different.The stem structure also showed certain differences.(2)Based on the characteristics of the stem and leaf,the principal component analysis and cluster analysis were performed using Statistica 6.0 analysis software,and the systematic relationships of 10 Euphorbia species were discussed.It was found that E.humifusa was most closely related to E.maculata,and E.jolkini was most closely related to the E.lunulata.On the contrary,E.kansui was distantly related to others.These results provided experimental basis for the classification of genus Euphorbia.