Objective:To evaluate the effect of active cycle of breathing techniques (ACBT) on respiratory muscle training in patients undergoing coronary artery bypass grafting (CABG) surgery.Methods:A quasi-experimental trial was performed. Patients were allocated to the control group or intervention group according to their time of admission. Patients who were admitted to hospital from January 2019 to April 2019 were assigned to the control group and patients admitted from May 2019 to October 2019 were allocated to the intervention group. The control group ( n=84) received routine perioperative care, and the intervention group ( n=82) received ACBT in addition to routine perioperative care. Patients in both groups were trained 3 to 5 times a day throughout their stay in the hospital. The primary outcome measure was maximum inspiratory pressure (MIP), peak of expiratory flow (PEF), forced vital capacity (FVC). Other outcomes included the postoperative pulmonary complications (PPC), days of postoperative hospital stay. Results:The MIP, PEF, FVC value of the control group 3 days after extubation were (64.77±9.80) cmH 2O (1 cmH 2O=0.098 kPa), (139.52±23.74) L/min, (1.07±0.20) L, the intervention group were (69.89±10.92) cmH 2O, (150.37±28.65) L/min, (1.15±0.22)L, the differences between the two groups were statistically significant ( t values were -3.177,-2.657,-2.409, P <0.05). The MIP, PEF, FVC value of the control group 5 days after extubation were (71.13±8.64) cmH 2O, (270.48±44.36) L/min, (2.02±0.29) L, the intervention group were (74.72±12.48) cmH 2O, (287.07±58.61) L/min, (2.21±0.35) L, the differences between the two groups were statistically significant ( t values were -2.161,-2.060,-3.605, P <0.05). The days of postoperative hospital stay of control group and intervention group were (8.15±0.98) and (7.80±1.23) d, there were significant differences ( t value was 2.021, P <0.05). Conclusions:ACBT is an effective and economical pulmonary rehabilitation method, it has effect on Respiratory Muscle Training in Patients Undergoing CABG surgery.