Osteoarthritis is one of the most common arthropathy in the world, and the artificial knee replacement surgery becomes one of the major measures to cure the severe pathological changes in the knee. The soft tissue balance is very important to prolong the artificial joint’s life in the total knee replacement (TKR), but now the balance is mainly depended on the surgeon’s experience, so the result is not confident. In order to meet the quantitative soft tissues balance measurement requirement in the TKR, a new soft tissues balance measurement method and system have been developed based on the load sensor technology, computer graphics technology and the precise mechanical design in this paper. In the system, six precise load sensors have been embedded in the front end measure device, which will be inserted into the knee joint. Each sensor is responsive to a force generated between the condyle and the device, and the pressure of the sensors represents the force of the posterior, middle, and anterior position in the medial/lateral part of the knee joint. Furthermore, the device has the function that can change the distance between its upper and lower plate by the mechanical structure for adjusting the space in the knee joint. The preliminary test shows that the measurement system can accomplish the force measurement and the distance adjustment in the knee joint, and display the data of the force distribution in three-dimensional manner in real-time. Otherwise, all the reliable force and distance data during measuring saved can be provided for the modeling of the knee joint dynamics.