Abstract: The leaf structure of Populus qiongdaoensis T. Hong et P. Luo sp. nov. and P. adenopoda Maxim. were studied in the light microscope, the fluorescence microscope and the scanning electron microscope. The differences between them are as follows:Populus qiongdaoensis The upper epidermis is uniseriate. The sponge parenchyma cells are arranged loosely and the axes of its long cells are parallel to the leaf surface. Stoma is sunken or not sunken. The outer walls of the papillae subsidiary cells forming long peristomatal rims which overlap the guard cells.The cuticular striae of stomatal apparatus are coarse and spinous. The outer wall of the lower epidermis is sac-like with short spines. Populus adenopoda The upper epidermis is biseriate. The sponge parenchyma cells are arranged compactly and the axes of its long cells are perpendicular to the leaf surface. stoma is level and never sunken. The outer walls of the subsidiary cells with short rims which always not overlap the outer stomatal rims.The striae of the stomatal apparatus are fine and numerous and extended as lateral wings which connect with the wavy striae of lower epidermal cells.