Objective To explore the effects of morphine on the terminal of primary afferent fiber distributing in spinal lamina Ⅱ after the sciatic nerve crush. Methods The positive reactive areas of fluoride-resistant acid phosphatase(FRAP) at spinal lamina Ⅱ were measured by the FRAP histochemistry and microcomputer image analysis techniques, after sciatic nerve was injured 15 days and 30 days both in morphine and control groups of rats. Results The positive reactive areas of FRAP at spinal lamina Ⅱ were depleted on different degree in two groups of rat after sciatic nerve was injured. The positive reactive areas of FRAP were greater 40% on injured sciatic nerve in 30 days than in 15 days in control group. In morphine group, the positive reactive areas of FRAP were larger 22% on injured sciatic nerve in 30 days than in 15 days; simulaneously also were bigger 19% than on injured sciatic nerve 30 days of control group.Conclusion The positive reactive areas of FRAP at spinal lamina Ⅱ show recovering enlargement as the surviving time lengthens in both groups of rats injured sciatic nerve.Morphine may enhance the positive reactive area of FRAP at spinal lamina Ⅱ in rat of sciatic nerve crush.