Abstract: Objective To study the protective effect of piperine on H₂O₂-induced abnormal transient outward potassium current（I_to） in single rabbit atrial myocyte. Methods Effect of H₂O₂（50μmol/L） and piperine（7μmol/L） on I_to in single rabbit atrial myocyte was analyzed using the whole cell patch clamp technique. Results Piperine（7μmol/L） had no significant effect on I_to and its transient outward potassium channel dynamics.The peak value of I_to in rabbit atrial myocytes decreased to（32.8±2.0）pA/pF from（39.3±5.4）pA/pF（P＜0.05）,the current-voltage curve of I_to was shifted down,the channel steady-state activation curve of I_to was shifted to the right,the steady-state inactivation curve and the recovery time of I_to from inactivation did not change,the closed-state inactivation of I_to was accelerated,when H₂O₂（50μmol/L） was applied.Piperine（7μmol/L） significantly alleviated the inhibitory effect of H₂O₂ on I_to and its transient outward potassium channel dynamics（P＜0.01）. Conclusion Piperine can alleviate H₂O₂-induced abnormal I_to in rabbit atrial myocytes.