Abstract: To evaluate the effects of exogenous glycine betaine (GB) and CaCl2 on some physiological indexes of tobacco plants in the condition of heat and drought stresses, a pot experiment was conducted. Yunyan 85 was selected as the tobacco cultivar. The results indicate that spraying exogenous GB and CaCl2 could significantly increase the biomass of tobacco, and the exogenous GB treatment could significantly increase the content of chlorophyll, SOD and POD activities and maintain higher free proline content under heat and drought stresses, whereas the membrane permeability and MDA content in tobacco plant are low. The exogenous CaCl2 treatment on tobacco leaves could significantly increase the content of chlorophyll, SOD and POD activities and sustain higher free proline content, and significantly decrease levels of membrane permeability and MDA content. After a period of recovery growth, the contents of chlorophyll, SOD and POD activities of Yunyan 85 tabacco plants with exogenous GB, CaCl2 and H2O treatments are increased at different degrees, whereas MDA contents, free proline contents and membrane permeability are decreased. According to these results, it is thought that GB and CaCl2 have constructive effects in decreasing the injury caused by co-stresses of heat and drought and increasing the heat and drought resistance of tobacco plant.