Traditionally heparin is adapted according to total body weight (TBW) to providing anticoagulation during cardiopulmonary bypass (CPB), but it may be inaccurate in some patients. The medical records of 100 adult patients who received CPB in Tongji Hospital of Tongji Medical College Huazhong University of Science and Technology over a 10-month period in 2017 were included in the retrospective study. An unfractionated heparin (UFH) bolus of 300 IU/kg TBW was injected before initiation of CPB followed by additional doses (50 to 100 IU/kg) to maintain a target activated coagulation time (ACT) of at least 480 s. We used TBW, ideal body weight (IBW), lean body weight (LBW), or body mass index (BMI) to establish and evaluate a linear model of ACT and the amount of heparin respectively. The linear fit effect of the model based on BMI on the original data is better than the others. As the instruments to measure heparin concentration is unavailable in most medical institutions in China. The new linear model based on BMI is helpful to estimate a more individualized heparin dosage in the heparinized phase and to provide useful reference to the amount of remaining heparin in the neutralization phase.