Objective To study the toxicity of XTA on ventricular myocardial cells and its mechanism.Methods Cyclical perfusion was acutely used to detach the mature guinea pig myocytes.The activity of CK and LDH in a medium of myocardial cells was measured at 30,60,120 and 180 min after treated by XTA of 1μmol/L,10μmol/L, 100μmol/L and 1mmol/L.Rates of cell viability and apoptosis were also measured .The protein content and Na + K +ATP enzyme activity of the myocardial cells were measured as well.An electron microscope was used to investigate cell nucleus and organelle morphology.Results The release of CK,LDH and protein from the myocardial cell were increased gradually after administering XTA of 100μmol/L and 1mmol/L to the cells; cell activity decreased and the activity of Na + K + ATP enzyme decreased gradually. There were significant differences between XTA of 100μmol/L,1mmol/L and control group( P <0.01).Conclusion Gui nea pig ventricular myocardial cells are only injured after administering 100μmol/L and 1mmol/L concentrations of XTA higher than the effective concentration of the drug for 30min.