【Abstract】 Objective To investigate the effect of intraperitoneally administration of pentoxifylline on the development of hyperalgesia and the activation of glial cells in a rat model of postoperative pain . Methods Sixty male SD rats weight 190~220g were randomly divided into 2 groups: control group (NS group) and treatment group(PTX group), in which 50mg/kg saline vehicle or pentoxifylline treatment (n=30) was given by the intraperitoneally route 15min before surgery and continued daily to day 5 operation, respectively.The animal model of postoperative pain was established by incisioning hind paw. cumulative pain score and paw withdrawal threshold were measured at 1 day before operation and then at 1, 2, 3, and 5 hours and 1, 2, 3, and 5 days after operation. Spinal cord tissue samples from rats were taken for analysis of glial fibrillary acid protein(GFAP) and ionized calcium bindingadaptor molecule-1(Iba-1) expression by means of immunohistochemistry at the following times after operation: 1, 2, 3, and 5 days. Results ①At the following times after surgery: 1,2,3,5 hours and1,2d,3 days, the cumulative pain score were 2.98±0.43,3.96±0.84,6.65±0.57,8.68±0.74,10.28±0.48,7.05±0.68 and 5.65±0.54 in the PTX group respectively, less than the NS group with 4.06±0.67,6.09±0.18, 8.82±0.24, 11.08±0.56,13.12±0.23,9.56±0.78 and 7.82±0.67(P<0.05).② At the following times after surgery: 1,2,3,5 hours and 1,2 and 3 days,the PWT were 5.84±1.60,5.25±1.17,4.47±0.6,4.90±0.48,5.25±1.1,7.60±1.8 and 10.49±1.6 in the PTX group respectively, more than the NS group with 2.48±0.87,2.14±0.56,2.08±0.5,2.19±0.3,2.37±0.56,4.54±0.96 and 8.13±1.49(P<0.05).③The GFAP expression in the spinal cord tissue at the following times after surgery: 1,2 days and 3 days were 181.21±4.18,205.67±4.26 and 230.24±3.24 in the PTX group respectively, lower than the NS group with 244.12±4.9,258.60±4.12 and 276.27±3.48(P<0.05).④The Iba-1 expression in the spinal cord tissue at the following times after surgery: 3 days and 5 days were 168.24±3.24 and 170.66±3.99 in the PTX group respectively, lower than the NS group with 230.27±3.48 and 205.28±4.05(P<0.05).Conclusion pentoxifylline can attenuate the process of mechanical allodynia in a rat model of postoperative pain, the main mechanism may be inhibiting glial cells activation in the spinal cord.