An automatic impact reduction device is provided to prevent a first damage of a snow removing plate and a second damage of a vehicle. An automatic impact reduction device comprises: a snow removing plate moving according to the operation of a pair of steering cylinder(5,5a); a power unit assembly(10) pumping the fluid pressure of a pressure-oil tank(13) in order to discharge; a main control block(20) installed between a supply line(P) and a first or a second hydraulic lines(6,7), having a direction control valve(25) controlling the hydraulic flow and redirection; a pair of emergency bypass lines(30,30a) connected between the first and the second hydraulic line; and a safety valve block(40) having a pressure control valves(45,45a), installed at an emergency bypass line.