An anti-collision device for a plasma vertical cutting gun including a lifting frame of a plasma cutting machine; a connection mechanism; a fixing plate of a cutting gun fixed on the connection mechanism; a concave support plate connected with the lifting frame of the plasma cutting machine; and a proximity switch mounted on the concave support plate. The connection mechanism is mounted between the lifting frame of the plasma cutting machine and the fixing plate of the cutting gun. A contact surface between the connection mechanism and the concave support plate matches. One side of a joint plane between the connection mechanism and the concave support plate is of ferromagnetic materials and the other side is provided with a magnet, thereby attracting each other to realize a magnetic connection. The anti-collision device has comprehensive functions, convenient installation, reasonable structure, and short response time in case of impact.