The invention relates to a distal femur osteotomy positioning and guiding device and a positioning method thereof. The distal femur osteotomy positioning and guiding device comprises a positioning device and a measuring device. The positioning device comprises a first positioning plate, a screen plate, a femur cutting groove, a connection block, an osteotomy guide block, a fixing screw and a positioning screw. The measuring device comprises a first measuring plate, a second measuring plate and a pushing nut. The distal femur osteotomy positioning and guiding device has the advantages that osteotomy thickness can be measured accurately, osteotomy direction and thickness can be accurately quantified by inserting the positioning screw into the screen plate, the angle of the osteotomy face on the vertical plane is adjusted through selection of the positioning screw at different angles to meet preoperative design requirements, and finally, personalized accurate TKA (total knee arthroplasty) osteotomy is realized; the extramedullary positioning technology is adopted, so that interference on femur marrow cavities is avoided, intraoperative bleeding is reduced, surgical effect is improved, and surgical risk is lowered.