In this study, the morphology, physiology and transcriptome of different types of leaves were measured in adult trees of Silver Poplar, which provided a reference for revealing the maturation effect. The main results are listed: (1) The leaf morphology at long branches and short branches was significantly different, and the leaves in different parts overlap to a large extent. (2) The photosynthetic pigment content in different parts of leaves was significantly different, and the content of chlorophyll a and total chlorophyll in the lower leaves were significantly higher than those of the upper and middle parts. There were significant differences in antioxidant enzyme activities among different parts of leaves. The SOD enzyme activity in the lower leaves was significantly higher than that in the upper and middle parts. The MDA content was manifested as the middle > upper > lower part. (3) The nutrient content in different parts of leaves was significantly different. The starch content in lower leaves was significantly lower than that in upper and middle leaves; The IAA content of the leaves in different parts increased with the decrease of height, and the ABA content was the middle > the upper part > the lower part; The IAA and IAA/ABA of leaves at the long branches were significantly larger than those of the short branches, and the ZR content showed an opposite trend. (4) Based on transcriptome data, the number of differentially expressed genes (DEGs) between leaves in different parts were less than that between different types of leaves. (5) GO and KEGG enrichment analysis in pairwise comparison showed that the DEGs in upper long branch (SC)-VS-lower long branch (XC) and the upper short branch (SD)-VS-lower short branch (XD) were significantly enriched in the photosynthetic pathway. Of them two genes were annotated both encoding psbR protein and their transcripts in the lower leaves were upregulated. In addition, by analyzing the genes involving in IAA transduction process, the upregulation on the gene expression was observed in the leaves of short branches.