The invention discloses a principal shaft temperature control system of a high-speed grinding roll grinder, which comprises a principal shaft, a radial front bearing, a radial back bearing, a main oiltank, a front temperature sensing device, a back temperature sensing device and a control system; the radial front bearing and the radial back bearing are sleeved at outsides of two ends of the principal shaft, a front cooling slot and a back cooling slot are arranged on the radial front bearing and the radial back bearing; an oil outlet of the main oil tank is connected to oil inlets of the front cooling slot and the back cooling slot through a pipeline; oil outlets of the front cooling slot and the back cooling slot are connected with an oil returning opening of the main oil tank through the pipeline; the front temperature sensing device and the back temperature sensing device capable of sensing the oil temperature are arranged on the oil outlet ends of the front cooling slot and the back cooling slot; the front temperature sensing device and the back temperature sensing device are in electric connection and communication with the control system, the control system controls the output volume of the oil pump of the main oil tank. The principal shaft temperature control system has the advantages of guaranteeing stable temperature of a principal shaft system of a machine tool and ensuring the running stability of the high-speed principal shaft system.