Psoralea corylifolia L. fruit extracts exhibited osteoblastic proliferation stimulating activity in UMR106 cell line cultured in vitro. The flavonoids of corylin and bavachin were isolated and identified as active principles by activity-guided fractionation. The results suggested that Psoralea corylifolia L. fruit extracts and corylin and bavachin might stimulate bone formation or have potential activity against osteoporosis.