The utility model provides a mathematical teaching ruler, which belongs to the technical field of mathematical teaching appliances. The mathematical teaching ruler can solve the problem that the existing ruler can only measure length of a straight line segment. The mathematical teaching ruler comprises a shell body and a straight ruler provided with scales, the shell body and the straight ruler are connected with a pulley through a rotating shaft with two open ends, a pressure sensor, a display screen and an utility knife blade are arranged on the shell body, a displacement sensor is arranged on each of the knifepoint and the knife back, the distance that the displacement sensors move can be displayed on the display screen, and through holes distributed along the length direction of the straight ruler are formed in the straight ruler. According to the mathematical teaching ruler, the displacement sensor on the knife back is aligned to one end of a line segment to be measured, thus the distance that the displacement sensor moves, namely, the length of the line segment can be displayed through the display screen by extruding the knife back; or the displacement sensor on the knifepoint is used, and paper is cut through the knifepoint; or the straight ruler is used for measuring straight line segments; or a finger is inserted in the rotating shaft, a pen point is inserted in the through hole, and a circle can be drawn by rotating the straight ruler around the rotating shaft, therefore, the mathematical teaching ruler is multi-purpose.