We investigated phenotypic variation of Populus simonii from five provenances in northern China. Our results show that significant differences exist between plants of different provenances in morphological and physiological traits, except for leaf-stalk length and the number of leaf margins. The coefficient of variation for all traits ranges from 14.77% to 81.49%. The mean phenotypic coefficient of differentiation (V ST ) is 47.1%, which means that the variation within provenances is the major source for phenotypic variation in P. simonii. Given our cluster analysis of provenances based on an average linkage computing method, the five provenances of P. simonii investigated could be divided into three groups. Our results provide a theoretical basis for genetic resource conservation and provenance selection of natural P. simonii in northern China. We investigated phenotypic variation of Populus simonii from five provenances in northern China. Our results show that significant differences exist between plants of different provenances in morphological and physiological traits, except for leaf-stalk length and the number of leaf margins. The coefficient of variation for All mean traits ranging from 14.77% to 81.49%. The mean phenotypic coefficient of differentiation (V ST) was 47.1%, which means that the variation within provenances is the major source for phenotypic variation in P. simonii. Given our cluster analysis of provenances based on an average linkage computing method, the five provenances of P. simonii could could be divided into three groups. Our results provide a theoretical basis for genetic resource conservation and provenance selection of natural P. simonii in northern China.