To better study hip and knee replacement, 50 eligible hip and knee patients from March 2020 to April 2021 were selected. A 1 : 1 scale solid model was printed with CT thin-layer scanning data assisted by 3D printing technology to evaluate the ankle function of patients six months after surgery. The results showed that the 3D rapid prototyping time of the 1 : 1 fracture model in 50 patients was 3-4 hours. The operation time was 70–90 min, and the average operation time was 80 min. The actual application in operation was consistent with that in the simulation of the 3D printing model, after surgery, and there was no infection of incision soft tissue or loss of reduction in all 50 patients. CT thin-layer scan data aided 3D printing technology can help clinical hip and knee replacement simulation and planning, improving surgery’s accuracy and safety.