The invention discloses a back end tool-free mounting bracket for a server machine cabinet sliding rail, and can solve the problem that mounting requirement of a thin type server machine cabinet sliding rail cannot be satisfied by the existing back end tool-free mounting bracket due to large structural size and high mounting space requirement. The back end tool-free mounting bracket comprises a back bracket fixedly mounted at the back end of the sliding rail; a positioning assembly is arranged at the back end of the back bracket; the back bracket is positioned at a mounting position of the server machine cabinet through the positioning assembly; the back end tool-free mounting bracket is characterized by also comprising an elastic locking part; the elastic locking part comprises a locking sheet, a pin shaft and a tension spring; the locking sheet is rotationally mounted on the mounting plane of the back bracket through the pin shaft; a clamping hook is arranged at the back end of the locking sheet, and the clamping hook end runs through the positioning assembly from front to back; the tension spring is tightly arranged on the pin shaft in a sleeving manner; and one end of the tension spring is fixed on the locking sheet while the other end of the tension spring is movably connected with one side wall of the back bracket.