Abstract: Aimed at the problems of the anterior cruciate ligament(ACL) reconstruction in knee joint,such as deficiency in effective effect evaluation and insufficiency in operation safety,a zero gravity based force-measuring robot is developed to measure the pre-and post-operative tension of the knee joint ACL.The requirements for the robot's configuration and control are analyzed with regard to the ACL operation environment.Then the mathematical model of the ACL lateral force is deduced.The mechanical configuration and the control system design of the force-measuring robot for knee joint ACL are presented in detail.Lastly,experiments on measuring precision of the mandril displacement and force,and the post-operation evaluation on the ovine bone,are implemented.The results show that the robot is effective for ACL reconstruction evaluation and the mathematics model of ACL force in lateral direction is valid.