Objective To illustrate the correlation of body mass index (BMI) with stable dose of warfarin, and analyze the interaction between BMI and genotypes on warfarin dose. Methods A total of 427 consecutive stable anti-coagulated patients taking warfarin for the first time were recruited prospectively in our hospital from January 2010 to December 2014. Anticoagulant treatment related baseline and clinical data were collected. The correlation between weekly stable dose of warfarin and BMI was analyzed with Pearson correlation and multivariate linear regression analyses. The interaction between BMI and genotypes on the stable dose was analyzed with generalized linear model. Results BMI was positively correlated with the stable dose of warfarin (B＝0.47, 95%CI: 0.30?0.63, P＜0.001). The average dose of warfarin was increased by 0.40mg as BMI increasing by 1 unit. The equation of 10.47±0.40×BMI could predict the average weekly dose of warfarin. After stratified by genotypes, a positive correlation was found between BMI and stable warfarin dose among the CYP2C9*3 and VKORC1-1639G＞A carriers (r: 0.23 to 0.37, P＜0.05). There was no interaction between genotype and BMI (PCYP2C9×BMI＝0.87, PVKORC1×BMI＝0.58) on warfarin dose. Conclusion There is a positive correlation between BMI and stable dose of warfarin, which is not affected by genotypes. BMI and genotypes could influence warfarin stable dose collaboratively.