A preoperative planning program for hip replacement arthroplasty and an operation support jig are disclosed. The program causes the computer to execute an image inputting step of inputting a plurality of two-dimensional tomographic images of the lower limbs including the pelvis and the femur； an image reconstructing step of reconstructing a threedimensional image including the pelvis and the femur from the plurality of two-dimensional tomographic images； an artificial joint determining step of determining an artificial joint which is to be set to the acetabular cartridge of the pelvis； a setting position, and a setting direction from the three-dimensional image of the pelvis and the femur； a base jig setting step of setting a three-dimensional image of a base jig having three support columns which are in contact with three landmarks of the pelvis with respect to the three-dimensional image of the pelvis, and a parameter obtaining step of parameterizing and obtaining a direction of a line which passes through the upper end of a support column in immediate proximity to the acetabular cartridge of the pelvis in the three-dimensional image of the base jig and is parallel to the setting direction of the artificial joint.
