Objective To investigate the effect of dexmedetomidine (DEX) at different dosages on entropy index and hemodynamics during off-pump coronary artery bypass grafting (OPCAB). Methods From June 2016 to December 2017,0 patients undergoing OPCAB in the Department of Cardiothoracic Surgery of the First People′s Hospital of Yueyang were selected and randomized into groups A, B, C and D, with 20 in each group. Before anesthesia induction, groups B, C and D were given DEX at 0.5,0.7 and 1.0 μg/kg (50 ml, 10 min) respectively, and group A was given 50 ml saline. Subsequently, DEX was infused at 0.5,0.7, and 1.0 μg/(kg·h) respectively in groups B, C and D until chest closure, while group A was not treated. Mechanical ventilation was performed by anesthesia induction and followed by the right internal jugular vein puncture in 4 groups. The 4 groups were compared in the respects of response entropy (RE), state entropy (SE) and hemodynamics [central venous pressure (CVP), cardiac index (CI), intrathoracic blood volume index (ITBI) and systemic vascular resistance index (SVRI)]before administration (T₀), after intubation (T₁), after thoracotomy (T₂), after cardiac reposition (T₃). SPSS statistics 19.0 was used to analyze the data. According to the data type, single factor variance analysis, LSD-t test or χ² test was used for comparison among groups. Results Compared with T₀, RE and SE decreased significantly at T1-3 in all 4 groups, and compared with T₁, RE and SE decreased significantly at T2-3 in all 4 groups (P<0.05). RE and SE in group B, C and D were significantly lower than group A at T1-3, and RE and SE in group C and D were significantly lower than group B at T1-3 (P<0.05). Compared with T₀, CVP in group A, C and D increased significantly, and CI, ITBI and SVRI in 4 groups decreased significantly at T₁; CVP in group A, C and D increased significantly, and CI, ITBI and SVRI in group C and D decreased significantly at T2-3 (P<0.05). Compared with T₁, CVP in group A, C and D decreased significantly at T2-3, and CI, ITBI and SVRI in group C and D increased significantly, with significant difference(P<0.05). Compared with group A or B, CVP in group C and D increased significantly and CI decreased significantly at T2-3 (P<0.05). There was no difference between C and D in terms of those indices above all. Conclusion DEX is able to enhance anesthesia and entropy index of OPCAB, and a dosage at 0.7 μg/kg offers the best effect for hemodynamic stability.