To evaluate the osteotoxic effect of methylmercuric chloride(MMC) on cultured mouse osteoblasts, cytotoxic effect was measured by MTT assay after cultured mouse osteoblasts were incubated with various concentrations of MMC for 20 hours. The protective effect of Flos Carthami(FC) against MMC-induced osteotoxicity was also examined in these cultures. MMC decreased cell viability of cultured mouse osteoblasts remarkably in a dose- and time-dependent manners. In protective effect of FC was remarkably effective in blocking the osteotoxicity induced by MMC. From aboved the results, it is suggested that MMC induce osteotoxicity, and the selective herba extract such as FC is very effective in blocking MMC-mediated neurotoxicity on cultured mouse osteoblasts.