The invention relates to a special-purpose automatic testing machine for a braking force of a traction machine and a clamping and conveying device thereof. The machine comprises a wall board, a servo motor, a first-stage speed reducer, a second-stage speed reducer and an internal gear wheel. Protruding pressing plates are arranged at the bottom of one side of the wall board. The first-stage speed reducer is fixedly installed at the other side of the wall board or the second-stage speed reducer. A servo motor stator is fixedly installed at a first-stage speed reducer housing; an output terminal of the servo motor is connected with an input terminal of the first-stage speed reducer; an output terminal of the first-stage speed reducer installed at one side or the other side of the wall board fixedly by corresponding to the second-stage speed reducer is connected with an input terminal of the second-stage speed reducer; and the output terminal of the second-stage speed reducer is connected with the internal gear wheel fixedly and the internal gear wheel drives a traction machine rotor when work condition testing is carried out. Because the protruding pressing plates are arranged at the bottom of the wall board, two-stage speed reduction is carried out on the servo motor, the braking force of the traction machine can be obtained precisely by means of different moment modes. The testing machine has characteristics of small size, convenient operation, simple structure, and low cost.