The leaf anatomical features of 11 species grown in two greenhouses with strictly controlled temperature gradients and temperature+CO^₂ gradients was studied. The palisade parenchyma thickness, the spongy parenchyma thickness and the total leaf thickness were studied and analyzed with the purpose of demonstrating the effect of elevated CO₂ and temperature on the leaf anatomical characteristics. The results show that with the increase of temperature, the leaf thickness of C₄ species increases while the leaf thickness of C₃ species shows no constant changes; with the increase of CO₂, seven out of nine C₃ species increase their total leaf thickness, while the C₄ species decrease their leaf thickness. As for the change-trend on the multi-grades, plants exhibit linear or curve change. With the increase of temperature or both temperature and CO₂, on the 11 chosen species, different plants, even different branches in one plant, the leaf thickness varies greatly. These facts illustrate that the effect of increasing CO₂ and temperature on plants is species-specific. Since plant structures are correlated with their functions, the changes in anatomical leaf characteristics due to the elevated temperature and CO₂ may lead to functional differences.