Objective To investigate the effects of skin/muscle incision and retraction(SMIR)on mechanical paw withdrawal threshold and the ability of spatial learning and memory in immature rats after adulthood. Methods 27 male SD rats aged 3 weeks and weighing 60 ~ 80 g were randomly divided into 3 groups(n = 9):control group(group C),sham operation group(group Sham)and skin/muscle incision and retraction group (group SMIR). Group SMIR received operation for skin/muscle incision and retraction. Sham group received skin/muscle incision but no retraction.No surgery was operated on C group. Pain behavior was assessed by mechanical paw withdrawal threshold(MWT)to von Frey filament stimulation before and 1,3,7,12,22 and 32 days after operation.The effects of spatial learning and memory function were assessed by Morris water-maze test at 33 days after operation. Results Mechanical paw withdrawal threshold of group SMIR decreased 1 day after operation (P<0.05)and showed no significant difference before and 3,7,12,22,32 days after operation in 3 groups(P >0.05). In Morris water-maze test,compared with Sham and C group,the average escape latency in SMIR was sig-nificantly longer in the water maze navigation experiment(P < 0.01);the ratios of time and path in the quadrant of the platform were obviously lower in SMIR(P < 0.01). There was no statistical difference between sham and C group(P>0.05).Conclusion SMIR did not cause chronic pain but may cause a decrease in the ability of spatial learning and memory in immature rats.