Objective To investigate the effects of Xiaozhong Zhitong Ointment on remodeling and repair after skeletal muscle injury based on mRNA expression mechanism.Methods After rat model of injured gastrocnemius muscle with the method of contusion model were established,Xiaozhong Zhitong Ointment was used on rats of 4 d,7 d,14 d,21 d,quantitative PCR was used to detect MyoD mRNA and expression level of protein after the injury to explore the mechanism of muscle remodeling and repair for gastrocnemius muscle contusion model rat.Results The expression of MyoD mRNA and expression level of protein in the treatment group were significantly higher than that of the control group and model group（P<0.05）,which further confirmed the important role of Xiaozhong Zhitong Ointment in remodeling and repair process.MyoD was rise at 7 d after the injury,and it expression had maintained at a high level until 21 d after the injury.Compared with the model group,the expression peak was around 14 d,and then it returned to a general state.Conclusion After the rat gastrocnemius muscle get injured,in the natural repair process,the expression level of myogenic regulatory factors shows a trend of rising and dropping,the period of 7 to 14 days after the injury is in the peak of the expression.The expression level of MyoD shows a rising trend,and the decline trend of expression is still not obvious even at 21 d after the injury,so it is can be seen that Xiaozhong Zhitong Ointment can promote the expression of MyoD.Xiaozhong Zhitong Ointment can promote the expression of MyoD,and adjust the regeneration and repair of skeleton muscle,which suggest that Xiaozhong Zhitong Ointment can play a role of regenerating and repairing skeletal muscle after the injury through gene regulation.