Objective To investigate the effect and mechanism of action of human umbilical cord mesenchymal stem cell conditional medium（uMSC-CM） in promoting the healing of combined radiation and wound injury（CRWI）. Methods A total of 42 male C57BL mice were randomly divided into trauma group，CRWI control group，and CRWI treatment group，with 14 mice in each group. A mouse model of skin CRWI was established by whole body irradiation with 4 Gy γ-ray combined with full-thickness skin defect wound with a diameter of 1 cm. The mice in the CRWI treatment group were given intraperitoneal injection of 5 mg/kg uMSC-CM once every other day，while those in the other two groups were given injection of an equal volume of serum-free DMEM medium. Photographs and HE staining were used to assess wound healing；CD31 immunofluorescent staining was used to observe neovascularization；α-SMA immunohistochemical staining was used to observe cell migration；Masson staining was used to evaluate collagen deposition；Ki67 and TUNEL staining were used to measure proliferation and apoptosis；Western blot was used to measure the expression levels of apoptosis-related proteins and PI3K/AKT signaling pathway proteins. Primary skin fibroblasts of mice were divided into control group，irradiation group，and irradiation treatment group. Edu staining and colony formation assay were used to detect cell proliferation；cell scratch assay and Transwell assay were used to detect cell migration；flow cytometry was used to measure cell apoptosis；Western blot was used to measure the expression levels of PI3K/AKT signaling pathway proteins. Results In this study，uMSC-CM significantly promoted the healing of CRWI（P<0.05），and the histological results showed that uMSC-CM could promote angiogenesis，cell migration，and collagen fiber deposition in CRWI. Further analysis showed that uMSC-CM increased cell proliferation and reduced cell apoptosis in CRWI（P<0.05）. Western blot showed that uMSC-CM promoted the protein expression levels of phosphorylated PI3K and phosphorylated AKT（P<0.05）. In vitro cell experiments showed that uMSC-CM promoted the proliferation and migration of mouse dermal fibroblasts and reduced apoptosis after irradiation（P<0.05），and Western blot showed that uMSC-CM promoted the protein expression levels of phosphorylated PI3K and phosphorylated AKT after irradiation（P<0.05）. Conclusion This study shows that uMSC-CM accelerates CRWI wound healing，possibly by activating the PI3K/AKT signaling pathway to promote the proliferation and migration of fibroblasts and inhibit their apoptosis.