Abstract: In our report, Chronic Constriction Injury (CCI) rat model was established, intrathecal catheterization (i. t. ) and intraperitoneal injection (i. p. ) were employed, and the effects of two routes with different doses of morphine on MWT of CCI rats were compared. The results indicated that the morphine group of single i. p. (1 mg·kg^－1) after 1 h, 3 h treatments have similar analgesic effects with the morphine groups of single i. t. (1 μg· kg^－1), however, there are significant differences (P＜0.05) between the morphine group of single i. p. (1 mg·kg^－1) after 1 h, 3 h treatments and the morphine group of single i. p. doses of 0.5 mg·kg^－1 and 0. 1 mg·kg^－1 body weight, which suggested that the intrathecal catheterization (i. t. ) injection of morphine into Chronic Constriction Injury (CCI) rat model has the advantages of small dosage and better effects, and which could be used for screening drugs which are difficult to be extracted.