Abstract: In order to solve the problem of speed out of control of trackless rubber-tyred vehicle because of braking inefficacy when vehicle runs on the long and steep downgrade in inclined-shaft, the paper proposed using speed out of control protection device to increase safety of the vehicle running. Through analyzing the functions of the device, studying its constitute, working principle, interception device’s sufferance force and braking distance and other aspects, and according to the distance after speed out of control and braking distance of the vehicle, we gave the disposal method of the device in mine. Taking the WC20R（D） explosion-proof diesel trackless rubber-tyred vehicle as an example, assumes that the whole weight is 7 tons, climbing capacity is 12 degrees, running speed is 29 km/h, span length is 4.5 m, max speed is 70 km/h, deceleration is the range of 0.5g to 2.5g, by MATLAB, the result showed that the force of the interception device cable is set in 3.09 t to 11.84 t, braking distance is about 116 m to 23 m, the first interception device should be placed in the point which is 77 m below the slope.