The invention discloses a hydraulic cutter changing system of a machining center; the hydraulic cutter changing problem is solved; and a manipulator automatic cutter changing hydraulic system of the machining center realizes the transfer of power and energy between a tool magazine and a machine tool main shaft and the loading and the unloading of a tool changing device, and achieves the function of finishing automatic changing of a certain number of stored cutters. The automatic tool changing device can be hydraulically driven to save the auxiliary time of a numerical control machine tool, and can meet multi-procedure and multi-step machining requirements in once installation. The hydraulic system drives a manipulator of the machining center to automatically change the cutters to achieve the characteristics of quick cutter changing, short time, high repeated positioning precision, enough cutter storage quantity and stable work.