The invention relates to a safety support plate mechanism of hoisting equipment. The hoisting equipment is provided with a hoisting structural member and a box-shaped frame, wherein the hoisting structural member comprises a sliding rod piece. The safety support plate mechanism comprises a safety support plate, a cylindrical revolved body, a sliding arm and a roller wheel, wherein the safety support plate is hinged with the box-shaped frame of the hoisting equipment and pivoted to be closed and opened; the cylindrical revolved body is fixed on the safety support plate and provided with a long chute; the chute is provided with a spiral part and straight line parts positioned at the two ends of the spiral part; the sliding arm is rigidly connected to a sliding rod piece and provided with a free end; when the hoisting structural member is hoisted, the sliding arm is restrained to slide in a straight line; and the roller wheel is arranged at the free end of the sliding arm and can roll in the chute. When the hoisting structural member is hoisted, the sliding arm makes a straight line motion to drive the safety support plate to be opened; and when the hoisting structural member falls, the sliding arm makes a straight line motion to drive the safety support plate to be closed. Thus, when the safety support plate is in an open state, hoisting machinery can be protected from the danger of lateral inversion. The straight line parts at the two ends of the spiral part of the chute can be used for guaranteeing self-locking characteristics.