Abstract: Objective To study the role of heparin in early treatment of exertional heat stroke (EHS) in rats. Methods Sixty male SD rats were randomly divided into blank control group (group A, n=8), exertional heat stroke group (group B, n=26), and exertional heat stroke + heparin group (group C, n=26). A rat EHS + exercise model was established, then the survival rate of 10 rats randomly selected from group B and group C (group B1 and group C1) was analyzed. The remaining rats in groups B and C were randomly divided into group B2B3 and group C2C3 (8 in each group). Their platelets (PLT) and activated partial thromboplastin time (APTT) were calculated and their serum tumor necrosis factor-α(TNF-α) level was measured by ELISA. Results The 8 h survival rate was signifcantly higher in group C1 than in group B1 and signifcantly lower in group B2B3 and group C2C3 than in group A (P< 0.05, P< 0.01). The APTT was signifcantly longer in group B2B3 and group C2C3 than in group A (P< 0.01) and signifcantly shorter in group C than in group B (P< 0.01). The number of PLT was signifcantly higher in group C2C3 than in group B (P< 0.01). The serum TNF-αlevel was signifcantly higher in group B2B3C2 and group C3 than in group A and signifcantly lower in group C2C3 than in group B (P< 0.01). Conclusion Heparin pretreatment can increase the survival rate of EHS rats by improving their coagulation function, reducing their infammatory reactions and inhibiting their EHS progression.