Abstract: OBJECTIVE To investigate the effect of paeoniflorin (PF) on the pre-osteoblasts cell apoptosis and its related mechanisms， and to explore the effect of PF on zebrafish osteoporosis. METHODS In vitro， the pre-osteoblast cell line MC3T3-E1 cells were cultured and the dexamethasone (DEX)-induced cell apoptosis model was used to observe the protective effect of PF. The cell viability and cell apoptosis rate were detected by MTT assay and flow cytometry respectively. Western blot was used to detect the expressions of apoptosis-related proteins bcl-2 and Bax. The nuclear translocation of FoxO3a protein was detected by immunofluorescence assay. The prednisolone (Pred)-induced zebrafish osteoporosis model was established to observe the anti-osteoporosis effect of PF. The first vertebrae bone area of zebrafish was observed by calcein staining. qPCR was used to detect the mRNA expressions of osteoclast marker genes tartrate resistant acid phosphatase (TRAP)， cathepsin K (CTSK)， matrix metalloproteinases-9 (MMP-9) and osteoblast marker genes alkaline phosphatase (ALP)， runt-associated transcription factor 2a (Runx2a)， Sp7 transcription factor (Sp7). RESULTS PF alleviated the inhibitory effect of DEX on the MC3T3-E1 cell viability and reduced the cell apoptosis rate. Detection of apoptosis-related proteins revealed that PF significantly promoted Bcl-2 protein expression and increased the ratio of Bcl-2/Bax. PF also significantly inhibited the nuclear translocation of FoxO3a protein. Compared with the Pred group， PF increased the first vertebra bone area of zebrafish， inhibited the mRNA expressions of TRAP， CTSK and MMP-9， and promoted the mRNA expressions of ALP， Runx2a and Sp7. CONCLUSION PF inhibits pre-osteoblast apoptosis and alleviates zebrafish osteoporosis， which may be related to the increasing of Bcl-2/Bax ratio and inhibition of nuclear translocation of FoxO3a.