The invention relates to a gear with an overload protection function and belongs to the mechanical field. The gear is composed of a snap ring, a deep groove ball bearing, a ball, an inner ring, an outer ring, a spring, an end cover and a gear. The inner ring is provided with a flat keyway as a power input, the outer ring is arranged below the inner ring and is connected with the end cover through a spring, and the end cover and the inner ring are in threaded connection. The ball is placed in a hole in the edge of the inner ring, a semispherical hole is formed in the gear corresponding to the hole thereof, and the inner ring and the gear are connected via the deep groove ball bearing and are fixed by the snap ring. The gear has the beneficial effects that an effect of cutting of a torque is achieved when the torque of the gear exceeds an extreme torque, the gear can restore automatically to achieve the overload transmission protection function of the gear, such that mechanical accidents such as broken gear, rupture or damage of a transmission part and burn of a motor when the transfer working torque exceeds the allowed extreme torque are avoided. In the drawings, 1, snap ring; 2, gear; 3, deep groove ball bearing; 4, ball; 5, outer ring; 6, inner ring; 7, spring; 8, end cover.