Objective To study the influence of cardioplegic preconditioning on the contractile function of isolated inchemic/repperfused rat heart.Methods The Langendorff model of isolated perfused rat heart was used to study the effects of cardioplegic preconditioning on LVEDP,DP, dp/dt,-dp/dt,CF,protein contents and LDH activity before and after ischemia/reperfusion.Results Compared with the control group,cardioplegic preconditioning benefited the recovery of cardiac heamodynamics.It significantly delayed the onset of ischemic contraction.During the reperfusion period,it improved the recovery of contractile function and minimized the leakage of intracellular protein and lactate dehydrogenase.Conclusion cardioplegic pre-conditioning has protective effects against ischemia/reperfusion injury,and hence,might be a promising measure in clinical use.