Contents of chemical constituents, namely organic carbon(C), total nitrogen (N), total phosphorus (P), total potassium (K), of Populus euphratica desert riparian forest in Ejina oasis of northwestern China were compared among different months in growing season and different micro\|habitats, and the correlations among the chemical constituents were studied. Results showed that the ranges of C, N, P, and K contents in the leaves of  P.euphratica were 39.08%~46.16%, 0.28%~2.81%, 0.05%~0.18%, and 0.35%~2.03%, and the mean values were 43.51%, 1.49%, 0.102% and 1.17%, respectively. The ratios of C/N, C/P and N/P varied from 16.26 to 146.61, from 258.08 to 908.67, and from 2.89 to 26.67, respectively, and the mean values were 37.24, 466.27 and 15.14, respectively. The mean N content in the leaves of  P.euphratica was significantly lower than N content in deciduous tree in China, but their mean P contents were similar. The ratio of C/N in the leaves of P.euphratica was remarkably higher than that of terrestrial plants. The ratio of N/P indicated that growth of  P. euphratica was jointly limited by N and P nutrimental deficiency. The total content of leaf C, N, P, and K descended during growth season, and the maximum value appeared in May, the minimum appeared in September. The contents of C, N and K, and the ratio of N/P gradually increased from riparian lowland, flatland, sandpile, Gobi to dune, but the spatial pattern of C/N was opposite, and there was not significant spatial variation for P content. There were extremely significantly positive correlations between C content and N, K contents, respectively, and weakly positive correlation between C content and P content. The relationships of N and P with K were both significantly positive.