The invention discloses an absolute type ceramic piston rod displacement sensor. The absolute type ceramic piston rod displacement sensor comprises a cylinder barrel, a piston rod and a detection head; annular grooves with equal width, equal depth and unequal distance are formed in a metal rod body of the piston rod; the annular grooves and groove-free parts among the annular grooves are arrangedat intervals and are tightly combined to form absolute coding position information; the detection head is fixedly arranged at the joint of the cylinder barrel and the piston rod, and the detection head and the piston rod are arranged at intervals; and a giant magnetic resistor array module is arranged in the detection head and is configured to be used for detecting the radial arrangement of the grooves in the piston rod so as to obtain the absolute coding position information in the moving process of the piston rod. The absolute type ceramic piston rod displacement sensor has the advantagesthat absolute position measurement can be achieved, and power failure can be avoided; the coding distance is ultra-long, and the absolute type ceramic piston rod displacement sensor is suitable for measuring the stroke of hydraulic cylinders with various ranges; non-contact measurement can be achieved, and the abrasion can be avoided; and the absolute type ceramic piston rod displacement sensor can be widely applied to the field with hydraulic cylinders required to be used such as water conservancy and hydropower, industrial machinery, transportation, environment protection and military equipment.