The invention provides a hydraulic oil supply system for machine tool which rolls and strengthens torque shaft surface. The hydraulic oil supply system comprises a motor, a proportional constant-pressure variable stroke pump, a rough filter, an energy storage device I, an electromagnetic overflow valve, a high-pressure ball valve, a fine filter I, a fine filter II, an energy storage device II, a pressure sensor I, an electro hydraulic flow servo valve, a cut-off valve, a wind cooler, a returning oil filter, a pressure sensor II and a control unit; and in order to enable the oil pressure in an oil outlet of the electro hydraulic flow servo valve to be subjected to precise control, according to the hydraulic oil supply system, a preset control value and the pressure sensor II are used for returning a signal to generate a difference, so as to control a valve core of the electro hydraulic flow servo valve to move, and the precise control on the oil pressure of the oil outlet is achieved.