The application of 3D printing technology in the field of medicine is the navigation of surgery, which belongs to a kind of indirect use, through the CT scan, the human body’s bones, hard tissues reconstructed in the computer, the establishment of CAD models, and then through the 3D printing out. Printed out are resin, polymer materials, although not directly used, but can be used as a template for doctors to develop surgical programs for surgical navigation. Intuitively speaking, the doctor can not see the human bone structure, 3D scanning and printing out, can be held in the hand, and made into a 1:1 template, you can develop a surgical program to guide the doctor “how to go under the knife, how to cut the bone, it is a fixed template. Patient outpatient clinic first lower extremity MRI or CT examination, data collection, transfer to the computer, through the 3D printing out the patient 1:1 resin material knee joint, making the knee osteotomy mold, and measure the size of the knee prosthesis. During the surgery, each patient has an osteotomy mold and knee prosthesis that fits him/her only, thus achieving the ideal surgical result. It has the advantages of personalization, time-saving, accuracy and less trauma.