Objective：To investigate the effects of calcium peroxide（CPO）-loaded polycaprolactone（PCL）microparticles（CPO-PCL）on the proliferation and bone differentiation of adipose - derived mesenchymal stem cells（ADMSCs）in vitro under hypoxia. Methods：Rat ADMSCs were extracted and added with the prepared CPO-PCL particles for normal or osteogenic differentiation culture under hypoxia/normoxia environment. On the 7^th and 14^th days，cell proliferation，alkaline phosphatase（ALP）level，the calcification of nodulation，and the fluorescence intensity of Runt-related transcription factor 2（RUNX2），Osteocalcin and Osteopontin were examined by the MTT assay，alkaline phosphatase（ALP）kit，alizarine red staining and immunofluorescence staining，respectively. Results： Under hypoxia and osteogenic differentiation culture conditions，1.00% CPO - PCL microparticles significantly promoted ADMSCs proliferation（P ＜0.05），and CPO-PCL microparticles of 0.50% and 1.00% concentrations notably increased the production of ALP and calcium nodules（P ＜0.001），while enhancing the expressions of RUNX2，Osteocalcin and Osteopontin proteins（P ＜0.05）. Under hypoxia and normal culture conditions，1.00% CPO - PCL microparticles elevated ALP levels，increased the expression levels of RUNX2，Osteocalcin and Osteopontin（P ＜0.05）. Under normoxia and differentiation culture conditions，1.00% CPO - PCL microparticles increased the production of ALP and calcium nodules，and CPO-PCL microparticles of 0.50% and 1.00% concentrations promoted the expression levels of RUNX2 and Osteocalcin proteins（P ＜0.001）. Under normoxia and normal culture conditions，0.50% and 1.00% CPO-PCL microparticles up-regulated RUNX2，Osteocalcin and Osteopontin expression levels（P ＜0.05），but rarely affect osteoblast differentiation. Conclusion：CPO - PCL microparticles of 1.00% promote the proliferation and bone differentiation of ADMSCs in vitro under hypoxia and osteogenic differentiation culture.