Abstract: Objective To investigate the effect of heat stress on vascular endothelial growth factor A and related molecules in lungs of rats. Methods Thirty male SD rats were randomly divided into three groups: non-HS group (n=10), HS + 15-minute-recovery group (n=10) and HS + 3-hour-recovery group (n=10).Two heated groups of animals were put in a folded heating pad with general anesthesia. Once their core temperature (Tc) elevated to 42℃, the heated animals were allowed to recover at a room temperature for 15 min and 3 h. Levels of vascular endothelial growth factor A (VEGF-A) and related molecules of the lung homogenate were detected by enzyme-linked immunosorbent assay. Results Compared with the non-HS group, the levels of VEGF-A and transforming growth factor beta1 (TGF-β1) increased significantly in the HS + 15-minute-recovery group, while decreased noticeably in the HS + 3-hour-recovery group. The level of pre-inflamatory cytokine TNF-α slightly increased in the HS + 3-hour-recovery group. However, no significant difference of the pre-inflamatory cytokine IL-6 was found among the three groups. Conclusion The level of VEGF-A which may be only affected by heat injury in the early stage of heat stress decreases below the normal level after a transient elevation, and it plays a crucial role in the development of acute lung injury (ALI) in rats under heat stress.