Abstract: In this study, the protective effects of (-)R·R-daurisoline and its three optical isomers on ischemic injury in cultured PC12 cells induced by treating cells with NaCN in glucose-free medium were investigated. Cell viability was measured using MTT assay. The results indicated that these compounds, especially (-)-S·R and (+)-R·S isomers were found substantially to attenuate ischemic injury in PC12 cells in a dose-dependent manner. The IC₅₀ values of (-)-R·R,(-)-S·R,(+)-R·S and (+)-S·S isomers were shown to be 18.6×10^-6, 2.4×10^-6, 5.9×10^-6 and 90×10^-6 mol·L^-1, respectively. Intracellular free Ca²⁺ concentration in PC12 cells was measured using AR-CM-MIC cation measurement system with Fura-2/AM as Ca²⁺ fluorecent indicator.(-)-R·R-daurisoline and its three optical isomers: (-)-S·R, (+)-R·S and (-)-S·S were found to markedly inhibit the increase of cytosolic free Ca²⁺ concentration induced by NaCN (20 mmol·L^-1) in a dose-dependent manner.Their IC₅₀ were found to be 3.55×10^-6, 0.59×10^-6, 1.29×10^-6 and 24.3×10^-6 mol·L^-1　 respectively. It is suggested that the cytoprotective effects of daurisoline and its isomers were mediated by blocking Ca²⁺ influx into cells.