Abstract: An automatic stop mechanism for a rolling door includes two brake members mounted to the stop member which is removably engaged with the fixture, the stop member having a flange disengagably contacting the inclined flange to normally stop the rolling door, a handle pivotally connected to the fixture and connected to the first member and the second member so as to shift the stop member along the shaft of the motor, the two brake members each having a brake pad and located within the motor casing, when the rolling door runs downwardly fast and the normal stop mechanism fails, the two brake members are expanded due to the eccentric force to stop the door by the two brake pads contacting the motor casing.