Objective To investigate the effect of rapid maxillary expansion （RME） on sagittal soft and hard maxillofacial tissue in growing children. Methods In this retrospective study， children aged 6-12 years treated in Shanghai Stomatology Hospital from Jan 2018 to Dec 2020 were employed as subjects. Of the subjects， 40 patients treated with RME were as the experimental group， 27 patients presenting individualized malocclusion were as the control group. Lateral cephalogram was taken before （T0） and 2 years after treatment （T1）. The images were imported into Dolphin Imaging’s cephalometric measurement software， and the results were statistically analyzed using SPSS 22.0 software. Results Statistically significant differences were observed in all measurements before and after treatment in both two groups. A comparative analysis revealed that SNB value increased and ANB value decreased in the experimental group after treatment， while the changes in the control group were significantly smaller than those in the experimental group （P<0.05）， indicating that RME is beneficial to the growth and development of mandibular in sagittal direction. Among the dentoalveolar measurements， statistically significant differences （P<0.01） were observed in U1-SN （upper incisor to sella-nasion angle）， U1-NA （upper incisor to nasion-A point angle）， U1-APog （upper incisor to A point-pogonion line distance）， and overjet between the two groups. These findings indicate that RME significantly reduces the inclination of the maxillary central incisors， while having no significant effect on the mandibular central incisors. Compared with the control group， RME significantly reduced upper lip prominence， lip space and upper central incisor exposure （P<0.05）， but had no effect on nose， chin and their correlation. Conclusion RME not only improved the prominence of the upper teeth and upper lip， but also facilitate the sagittal growth of mandibular in growing children.