Objective To make a histological evaluation of poly(dextrogyr-levogyr)lactide acide-triiodothy-ronine (PDLLA-T3) in sciatic nerve defect of rat. Methods Ninety SD rats were evenly divided into 3 groups (autograft group A, PDLLA-T3 group B and PDLLA group C). Group D was control group. The left sciatic nerves were cut off by operation and 1 cm-nerve-defect was set up. The specimens were collected 2 weeks,1 month and 2 months after the operation respectively, simultaneously the right sciatic nerves were collected as normal control group D. HE stainning, electron microscope, S100 immunohistochemistry, and Bielschowsky staining were done in all the specimens, the quantity and quality of the regenerated nerves were observed, and all the results were processed by image analyzer.Results Two weeks after the operation,histological observation indicated that the materials in groups B and C were not completely degraded. Transmission electron microscopic observationshowed that the myelin sheath was not thick and it was about 0.5 μm in thickness. There was no significant difference among the 3 groups. One month after theoperation, histological observation indicated that in group A the regenerated nerves passed through the scaffold and in the new nerves there were regenerated blood vessels. The materials in groups B and C were not completely degraded. S-100 immunohistochemical observation and Bielschowsky staining showed that in groupB PDLLA-T3 repaired the defect successfully and the regenerated nerve myelinsheath was 1.81±0.19 μm in thickness. The effect in group B was better thanthat of groups A and C (P＞0.05). Two months after the operation, the materials in groups B and C were completely degraded. The quantity of the regeneratednerves in group B confirmed by S-100 immunohistochemical observation and Bielschowslcy staining was more than that in group C(P＜0.05) and close to that in group A. The regenerated nerve myelin sheath in group B was 2.15±0.27 μm in the thickness and was thicker than that in group C (P＜0.05)， but thinner than that in groups A and D (P＜0.05). Conclusion PDLLA-T3 can repair the defect of rat sciatic nerve with satisfactory quantity andquality of regenerated nerves.