Objective To evaluate the effect of dexmedetomidine on spinal p38 mitogen?activated protein kinase ( p38MAPK) expression during remifentanil?induced hyperalgesia in rats with incisional pain. Methods Forty?eight healthy male Sprague?Dawley rats, aged 6 weeks, weighing 220-250 g, were ran?domly divided into 4 groups ( n= 12 each) using a random number table: control group ( group C) , inci?sion pain group ( group IP ) , incision pain + remifentanil group ( group IP+R ) , and incision pain +remifentanil + dexmedetomidine group ( group IP+R+D) . After successful establishment of the model of in?cisionsal pian, remifentanil 1?0μg∕kg was infused for 4 h via the tail vein in group IP+R; remifentanil 1?0μg∕kg was infused for 4 h via the tail vein, and dexmedetomidine 10μg∕kg was simultaneously infused for 4 h via the jugular vein in group IP+R+D; the equal volume of normal saline was infused for 4 h via the tail and jugular veins in C and IP groups. The mechanical paw withdrawal threshold ( MWT) was measured at 24 h before operation ( T0 ) , and at 4, 6, 24 and 48 h after the end of drug infusion ( T1?4 ) . After meas?urement of MWT at T4 , the expression of p38MAPK was determined using immuno?histochemistry. Results was up?regulated at T4 in IP and IP+R groups ( P<0?05) , and no significant change was found in the MWT and expression of p38MAPK in group IP+R+D (P>0?05). Compared with group IP, the MWT was signifi?cantly decreased at T1?4, and the expression of p38MAPK was up?regulated at T4 in group P+R, and the MWT was significantly increased at T1?4, and the expression of p38MAPK was down?regulated at T4 in group IP+R+D (P<0?05). Compared with group IP+R, the MWT was significantly increased at T1?4, and the expression of p38MAPK was down?regulated at T4 in group IP+R+D ( P<0?05) . Conclusion The mecha?nism by which dexmedetomidine reduces hyperalgesia induced by remifentanil is related to down?regulation of spinal p38MAPK expression in the rats with incisional pain.