A navigation system and method for joint replacement surgery, the system comprising: a pre-operative planning module (1), configured to perform segmentation and reconstruction on the basis of acquired hip joint medical image data to obtain a hip joint three-dimensional model, and perform pre-operative planning to determine the position, size, and angle of a prosthesis placement; and a navigation alignment module (2), configured to determine the spatial position of the pelvis and femur on the basis of a pelvis reference frame and a femoral reference frame, perform alignment on the hip joint three-dimensional model on the basis of the spatial position relationship between a surgical probe and the pelvis reference frame and femoral reference frame to obtain a hip joint physical model, and control a surgical instrument clamping the prosthesis to place the prosthesis in the hip joint on the basis of the hip joint physical model. By means of the pre-operative planning of information such as the surgical access and prosthesis placement, and tracking the surgical instrument during the surgery by means of a spatial positioning method, the accuracy of surgery is improved and navigation support is provided to the physician, making the surgery safer and more efficient.