Abstract: Objective To compare the effect of interior heat needle therapy on morphology of chronic gastrocnemius muscle tendon injury and brain-derived neurotrophic factor（BDNF） level in rats. Methods Twenty-seven healthy male Wistar rats were randomly divided into injury control group（n=12）,interior heat needle therapy group（n=12） and normal control group（n=3）.Rat in normal control group and injury control group did not receive any treatment.A chronic soft tissue injury model was established.Three rats in injury control group and interior heat needle therapy group were killed 3,7,14 and 28d after treatment.Morphology of inured tissue and BDNF level were observed under optical microscope with immunohistological staining. Results The changes of morphology indicated that the tissue repair was better in interior heat needle therapy group than in injury control group.No significant difference was observed in tissue repair between the two groups 3d after treatment（P＞0.05）.However,the tissue repair was much better in interior heat needle therapy group than in injury control group 7 and 14d after treatment（P＜0.05） and less in interior heat needle therapy group than in injury control group 28d after treatment（P＜0.05）. Conclusion Interior heat needle therapy can significantly increase the basic fibroblast growth factor（BFGF） level and is thus effective for chronic soft tissue injury in rats.