OBJECTIVE To observe the effects of volatile oil of Rhizoma Acori Tatarinowii (VOSCP) on morphology and cell viability in cultured neonate rat cardiac myocytes. METHODS The cardiac myocytes were cultured by trypsin under cool treatment, and the cell purity was assayed with imminocytochemistry; Morphological changes were observed under phase contrast microscope after cardiac myocytes with VOSCP of different concentration for 24h in vitro, and the cell viability was examed by MTT assay. RESULTS The purity of cultured neonate rat cardiac myocytes was higher than 95%; VOSCP of different concentration could depress pulse frequency and 100-160 mg/L VOSCP can obviously improve the viability of cardiac myocytes. The relation of dose-effect relationship was a parabola whose peak was at the value of 140 mg/L. CONCLUSION VOSCP of proper concentration can depress pulse frequency and improve the viability of cardiac myocytes.