Abstract: Open-top chambers (OTC) were used to simulate temperature enhancement to explore the effects of global warming on plant height, biomass, the number of buds, antioxidant enzyme, free proline and net photosynthetic rate of Populus yunnanensis and P.szechuanica. Results showed that the average height, dry weight, and average internode length were increased in both P.yunnanensis and P.szechuanica in comparison with CK, whereas a significant increase was not observed in P.szechuanica. POD activity in leaves of P.yunnanensis and P.szechuanica was significantly decreased while free proline content was significantly increased. At the same time, the soluble sugar content in leaves of P.szechuanica was significantly redcued, in contrast, the MDA concentration in leaves of P.yunnanensis was significantly increased. Under the warming conditions, net photosynthetic rate (P_n), total chlorophyll as well as chlorophyll content were increased in both P.yunnanensis and P.szechuanica. Furthermore, the changes of chlorophyll content in P.szechuanica were more significant. As a result, it could be concluded that P.yunnanensis and P.szechuanica were able to adapt to temperature enhancement through internal adjustment, as manifested by increases of proline and chlorophyll as well as P_n. The different responses between P.yunnanensis and P.szechuanica to temperature enhancement indicated that P.szechuanica from the high-altitude might physiologically better adapt to global warming.