The utility model provides a self-operated type pressure-range automatic switching valve, which comprises a valve body and a piston. The valve body is equipped with a gas inlet, a low pressure gas outlet, a high pressure gas outlet, and a pressure channel leading to the rear end of the piston from the air inlet. The gas inlet, the low pressure gas outlet, the high pressure gas outlet and the pressure channel are respectively connected with the cavity of the valve body. The front end of the piston is provided with a spring. One end of the spring is kept stationary relative to the valve body and the other end of the spring abuts against the front end of the piston. The piston is equipped with a first sealing ring and a second sealing ring used for blocking the low pressure gas outlet and the high pressure gas outlet respectively. The piston has two state positions. When low pressure gas is let in through the gas inlet, the piston is placed at the first state position. The high pressure gas outlet is sealed and the gas inlet is communicated with the low pressure gas outlet. When high pressure gas is let in through the gas inlet, the piston is placed at the second state position. The low pressure gas outlet is sealed and the gas inlet is communicated with the high pressure gas outlet. Whether the different-range measuring channels of a pressure gauge are communicated with each other or not is controlled through the compressed movement of the piston. Therefore, the pressure measurement of two different ranges can be realized. Meanwhile, the damage of the high pressure to a low-range pressure gauge during the reverse purging process is also avoided.