A linear actuator with a contact type safety nut, comprising a central screw, a driving nut mechanism, and a safety nut mechanism, wherein the central screw has a screw raceway, the safety nut mechanism comprises a safety nut seat sleeved at the periphery of the central screw, characterized in that the safety nut further comprises hole channels pointing to the central screw are arranged on the safety nut seat, an elastic buffer element is arranged in each of the limit hole channels, a safety ball is arranged between the elastic buffer element and the central screw, the safety ball partially extends into the screw raceway to be partially positioned in the corresponding limit hole channel, and the safety ball is capable of rolling along the screw raceway and moving along the corresponding limit hole channel; and in that the plurality of limit hole channels are arranged on the safety nut seat along a circumferential direction of the safety nut seat, and the elastic buffer element and the safety ball are arranged in each of the limit hole channels; and in that thread teeth are provided on an inner wall of the safety nut seat, and the thread teeth extend into the screw raceway and are spaced from the central screw; and in that the limit hole channels are filled with oil, and a cross-sectional diameter of each of the limit hole channels is consistent with a diameter of the safety ball; and in that the limit hole channels pass through inner and outer side walls of the safety nut seat, the safety ball blocks an outlet of the corresponding limit hole channel close to the central screw, a plunger is detachably installed at an inlet of each of the limit hole channels far away from the central screw, the plunger blocks the inlet of the corresponding limit hole channel, and the elastic buffer element is positioned between the plunger and the safety ball; and in that a gap is provided between the safety nut seat and the driving nut mechanism, and forms an oil supplementing cavity, the oil supplementing cavity surrounds the central screw, and transfer hole channels for communication between the limit hole channels and the oil supplementing cavity are arranged in the safety nut seat. and in that the plurality of limit hole channels are arranged on the safety nut seat along a circumferential direction of the safety nut seat, and the elastic buffer element and the safety ball are arranged in each of the limit hole channels; and in that thread teeth are provided on an inner wall of the safety nut seat, and the thread teeth extend into the screw raceway and are spaced from the central screw; and in that the limit hole channels are filled with oil, and a cross-sectional diameter of each of the limit hole channels is consistent with a diameter of the safety ball; and in that the limit hole channels pass through inner and outer side walls of the safety nut seat, the safety ball blocks an outlet of the corresponding limit hole channel close to the central screw, a plunger is detachably installed at an inlet of each of the limit hole channels far away from the central screw, the plunger blocks the inlet of the corresponding limit hole channel, and the elastic buffer element is positioned between the plunger and the safety ball; and in that a gap is provided between the safety nut seat and the driving nut mechanism, and forms an oil supplementing cavity, the oil supplementing cavity surrounds the central screw, and transfer hole channels for communication between the limit hole channels and the oil supplementing cavity are arranged in the safety nut seat.