Objective To investigate the clinical effect of protraction combined with expansion in the treatment of 8-11 year old children with skeletal class Ⅲmalocclusion in mixed dentition. Methods Forty-eight children with skeletal class Ⅲmalocclusion (maxillary deficiency, normal mandibular development or mild mandibular excess) in mixed dentition who were treated at Nanchang First Hospital from June 2015 to December 2019 were selected as the research subjects. According to age, the children were divided into 8-9 year old group and ＞9-11 year old group, with 24 children in each group. Both groups of children were treated with protraction and expansion. Lateral cephalogram, recovery effect and related physiological structural changes were compared between the two groups. Results There were no statistically significances in sella-nasion-B (SNB) and lower incisor-mandibular plane (L1-MP) between the two groups at 6 months after treatment (P＞0.05). At 6 months after treatment, the sella-nasion-A (SNA), point A-nasion-point B(ANB), sella-nasion and palatal plane (SN-PP), mandibular plane-frankfurt horizontal plane angle (MP-FH) and upper incisor/sella-nasion (U1-SN) were larger than those before treatment, and angles between upper and lower central incisors (U1-L1) were smaller than those before treatment in the two groups. At 6 months after treatment, the SNA, the ANB, U1-SN and SN-PP in 8-9 year old group were larger than those in the ＞9-11 year old group, and the U1-L1 was smaller than that in the ＞9-11 year old group, the differences were statistically significant (P＜0.05). There was no statistically significance in MP -FH between the two groups at 6 months after treatment (P＞0.05). The effective recovery rate in 8-9 year old group was higher than that in the ＞9-11 year old group at 6 months after treatment, the difference was statistically significant (P＜0.05). The length of soft palate at 6 months after treatment in the two groups was shorter than that before treatment, and nasopharyngeal inner diameter at 6 months after treatment in the two groups was longer than that before treatment, the differences were statistically significant (P＜0.05). The nasopharyngeal inner diameter of 8-9 year old group at 6 months after treatment was longer than that of the ＞9-11 year old group,the difference was statistically significant (P＜0.05). Conclusion Protraction combined with expansion can effectively improve skeletal class Ⅲmalocclusion in 8-11 year old children in mixed dentition, and the treatment effect is better in 8-9 year old children.