Brake device for chain saw

The utility model discloses a brake device for a chain saw. The brake device is composed of a brake bracket, a hand protector, a spring, a cam, a brake reed assembly and a driven plate, wherein the brake reed assembly is provided with a brake reed and a guide pillar, and the spring sleeves the guide pillar; the brake device is characterized in that: after the brake reed is installed on the driven plate in a sleeving manner, one end of the brake reed is fixed to the brake bracket while the other end is fixedly installed on the guide pillar; the end part of the guide pillar always contacts the cam under the effect of the spring; when the hand protector is rotated, the cam is driven to rotate, the guide pillar stretches forwards along with the spring that stretches along with the rotation of the cam, and then the brake reed is pulled to clamp the driven plate, thereby achieving the braking function. The hand protector is a two-arm hand protector, which is easy to operate and high in reliability in braking and can effectively prolong the service life of brake parts. The brake device provided by the utility model has brake parts which are simple in structure, convenient to disassemble and assemble and high in reliability, and can effectively improve the safety of brake parts even the safety of the chain saw.