Objective:To evaluate the difference and correlation of activated clotting time(ACT) measured between Celite i-STAT- Ⅱ and clinical classical measurement method-Medtronic ACT Ⅱ. Methods:Sixty patients underwent elective cardiac surgery. We compared ACT values measured by Medtronic ACT-Ⅱ and Celite i-STAT- Ⅱ. Blood samples were obtained before establishment of extracorporeal circulation,after heparinization and protamine neutralization,respectively,and then measured by the two methods. Linear regression and Pearson correlation analysis were performed to assess the consistency of the two measured data. Bland-Altman plot was performed to evaluate bias. Results:Celite i-STAT-ACT value was 85 to 913 seconds and Medtronic ACT-Ⅱ value was 99 to 980 seconds,R2 = 0.96,regression equation:y = 7.86 + 0.86x,Pearson correlation coefficient:r = 0.98(P < 0.001). ACT value ranged from 480 to 999 seconds and had linear correlation,R2 = 0.65,regression equation:y = 108.82 + 0.72x,Pearson correlation coefficient:r = 0.80(P < 0.001). Bland-Altman plot showed that the results of the two methods had good consistency. Conclusion:In ardiac operation under extracorporeal circulation,ACT values measured by Celite i-STAT- ACT and Medtronic ACT-Ⅱ are acceptable clinically.