In a multi-touch interactive system, distinguishing between user's left and right hands is of great significance for recognizing multi-finger gestures and further fully exploring the potential of bimanual interaction. However, the function of left-right hand distinction is beyond the capability of most multi-touch systems. In this paper, a robust solution to the left-right hand distinction based on the anatomical structure characteristic of hand is presented. Firstly, guided by the basic principles of gesture designing, the interactive tabletop hand-arm triangle model is proposed based on the anatomical structure characteristic of hand. Secondly, multi-touch interactive tabletop same hand contact points clustering method and left-right hand recognizing method are given based on the triangle model. Then, the methods are integrated into MTDriver to detect and send contact points's left-right information to the multi-touch applications and new bimanual interactive technologies are demonstrated. Finally, evaluation shows that the solution can achieve high recognition accuracy and good time performance that could support fluency bimanual interaction on interactive tabletop.