Abstract: Objective: To compare compensatory sweating between T2-4 and T3-4 endoscopic thoracic sympathectomy in treatment of palmar hyperhidrosis, and thus to investigate the potential mechanism of the occurrence of compensatory sweating. Methods: One hundred and forty-six patients with primary palmar hyperhidrosis w ere divided into two groups: 66 with T2-4 sympathectomy(T2-4 group ) and 80 with T3-4 sympathectomy (T3-4 group ). And compare two groups of operation effect , compensatory sweating location and severity after 1 day and 6 month postoperation. Results: The effective rate was 100%, and the most common compensatory sweating parts were back and chest. The compensatory sweating incidence were 39% and 21% respectively, showed statistically significant (P＜0.05). There were 2 cases of severe compensatory sweating in T2-4 group, and T3-4 group without severe case after 1 day. The compensatory sweating incidence were 24% and 11% respectively, showed statistically significant (P＜0.05). There was 1 case of severe compensatory sweating in T2-4 group, and T3-4 group without severe case after 6 month. Conclusion: Lowering the level of sympathectomy for primary palmar hyperhidrosis result in less compensatory sweeting. T3-4 sympathectomy is an ideal operation method. Compensatory sweating may alleviate.