Objective: To investigate the effect of ultrasound-guided BTX-A injection in the treatment of cerebral palsy on children""s MAS score and analyze its relationship with SWE parameters. Methods: A retrospective analysis of the clinical data of 86 children with cerebral palsy diagnosed and treated from May 2016 to June 2019. Among them, 86 children with cerebral palsy were set up as the observation group and divided into group B according to different treatment methods ( Rehabilitation training) and group A (BTX-A injection therapy under ultrasound guidance based on rehabilitation training), 43 cases in each, 43 normal children were selected as the healthy control group; and Emean value (medial gastrocnemius, soleus muscle) , Semimembranous muscle), MAS score, CMFM-88 score, PROM, analyze the correlation between Emean value and MAS, and observe the AUC value of Emean value. Results: The Emean values of the medial gastrocnemius, soleus, and semimembrane muscle of the observation group were significantly higher than those of the healthy control group (all P<0.05). After 1 and 6 months after treatment, the MAS score, PROM and Emean values (medial gastrocnemius, soleus, semimembrane) of group A were lower than those of group B, while CMFM-88 score was higher than that of group B (all P＜0.05) . Pearson correlation showed that the Emean value of medial gastrocnemius, soleus, and semimembrane was positively correlated with MAS score (all P<0.05). ROC curve analysis showed that the area under the curve of the Emean value of the medial gastrocnemius, soleus, and semimembrane muscles was AUC (0.746/0.732/0.771, sensitivity 90.70/95.30/95.30, specificity 59.30/57.00/58.10, P<0.05) . Conclusion: The ultrasound-guided BTX-A injection has a significant therapeutic effect, which can reduce the stiffness of the muscle tissue while improving muscle spasm in children.