Objective To investigate the effect of different dose of -receptor antagonist CTOP on remifentanil-induced hyperalgesia in incisional pain rat model by observing rats' paw withdrawal thermal latency（PWTL）and the dynorphin expression in spinal cord. Methods Thirty male SD rats were randomly divided into 5 groups (n=6): control group (A), incisional pain group (B), incisional pain + remifentanil group (C), incisional pain + remifentanil + CTOP lower dose group (D), incisional pain + remifentanil + CTOP higher dose (E). All rats were anesthetized with intraperitoneal 5% chloral hydrate（350 mg/kg）. Ten min after administered intravenously with 0.4 ml saline in group A, group B and group C, with 0.5 μg/kg CTOP in group D and 0.5 mg/kg CTOP, rats in all groups except group A were underwent right hind paw surgery. Meanwhile, rats in group A and group B were infused intravenously with saline，and rats in group C, group D and group E were infused intravenously with remifentanil of 40 μg/kg by lasting 30 min. 24 h(T2) later,24 h later, all rats were sacrificed and spinal cord tissues were separated for detecting the expression of dynorphin by ELISA. PWTL was tested at time before anaesthesia (T0), 2 h (T2) and 24 h (T2) after paw surgery. Results PWTL were significantly lower in group C [(10.2±3.0) s at T1 and (6.2±2.6)s at T2] than that in group A [(13.3±2.4)s at T1 and (13.4±2.2) s at T2]and group B[（13.5±2.7s at T1 and (11.5±4.1）s at T2] compared with group A. Dynorphin expression in group C（172±17）ng/Lwere higher than that in group A （78±9）ng/Land group B（120±10）ng/L (P <0.05). Compared with group C,PWTL were higher and dynorphin were lower significantly in group D and E (P<0.05). There were different in the dynorphin expression between group D and group E. Conclusions In rat model of incisional pain, remifentanil could enhance postoperative pain, -receptor antagonist (CTOP) could reduce the hyperalgesia induced by remifentanil and the lower dose is more effective.