The present study was prospectively designed to assess the clinical effect of leukocyte-depleted blood cardioplegic solution (BCS) on myocardium during cardiac surgery with cardiopulmonary bypass (CPB). 30 adult patients scheduled for elective cardiac surgery were divided into control group (n＝15), which infused routine BCS, and leukocyte-depleted (LD) group (n＝15), which infused leukocyte-depleted BCS. Total and differential leukocyte counts in BCS, malondialdehyde (MDA) and troponin-T (TnT) concentrations in coronary sinus blood, and cardiac index (CI) were measured at preoperative and postoperative period. The BCS in LD group had less total leukocyte counts with neutropenia than that in control group (P＜0.01). MDA (3.70$pm$0.35 vs 5.90$pm$0.57 $mu$mol/L, p<0.05) and TnT (0.42$pm$0.03 vs 0.60$pm$0.09 ng/mL, p<0.05) were significantly low in LD group compared with control group, while LD group had higher CI (3.28$pm$0.16 L/min/$m^2$, p<0.05) than control group (2.69$pm$0.18 L/min/$m^2$). These results suggest that leukocyte-depleted blood cardioplegic solution has a better myocardial protective effect with less generations of oxygen free radicals and ischemia/reperfusion injury.