Seventeen morphological and physiological traits of Populus simonii were analyzed among and within five provenances distributed in northeastern and the North China. Analysis of variance for all traits showed that there were significant differences among provenances and individuals within provenances. The mean phenotypic differentiation coefficient (VST) for all traits was 47.11%, which meant that the variation within provenances was slightly higher than that among provenances. The analysis of correlation between the morphological and physiological traits of P. simonii and the geographical and climatic factors indicated that the variations among populations presented gradient regularity. In contrast to the low-elevation provenances, individuals from high-altitude provenances displayed high trees and large leaves. According to the UPGMA cluster analysis based on the Euclidean distance, five provenances of P. simonii investigated could be divided into three groups. The results provide theoretical basis for conservation and utilization of natural P. simonii genetic resources.