The invention relates to the technical field of medical apparatuses and instruments, in particular to a proximal-tibia osteotomy instrument assembly. The proximal-tibia osteotomy instrument assembly comprises an osteotomy positioning piece, an osteotomy module, a first adjusting device and an osteotomy supporting piece; the osteotomy positioning piece comprises a body part, a first bending part and a second bending part, wherein the first bending part and the second bending part are arranged at the two ends of the body part respectively, and a guiding groove is formed in the body part; the first adjusting device comprises a locking nut, a connecting rod, a connecting column and an elastic piece, one end of the connecting rod penetrates through the guiding groove and is connected with the locking nut, the other end of the connecting rod is connected with the connecting column, the connecting column is connected with the osteotomy module, and the elastic piece is arranged on the connecting rod and located between the connecting column and the osteotomy positioning piece; the osteotomy supporting piece comprises a second adjusting device, the second adjusting device is connected with the first adjusting device, the osteotomy supporting piece is used for supporting and assisting in fixing a whole instrument, the osteotomy plane can be accurately determined, the osteotomy requirement of installation of a tibial prosthesis is met, and the ideal effect of an operation is guaranteed.