The invention discloses an adjustable overflow valve with an automatic calibration function. The adjustable overflow valve comprises a shell. A flow channel is formed in the shell. A plug and a springseat are arranged in the flow channel. A first spring is arranged between the spring seat and the plug. The shell is provided with a conical adjusting portion and an opening provided with a thread. The side of the opening is in threaded connection with an adjusting sleeve. A plurality of slides are arranged on the adjusting sleeve in the radial direction, and the middle of the adjusting sleeve isprovided with an overflow channel communicating with an oil return connector. Adjusting plates are arranged in the slides, a plurality of second springs used for propping the multiple adjusting plates open are arranged between the adjusting plates and the end surfaces of the slides, and bevels matched with the conical adjusting portion are arranged at the front ends of the adjusting plates. A plurality of limiting protruding bars are arranged on the side, close to the flow channel, of each adjusting plate. An elastic ring is arranged on the spring seat. An iron block is arranged on the springseat. The shell is provided with an electromagnet matched with the iron block. According to the overflow valve, the overflow pressure of the overflow valve can be adjusted, the setting pressure can still be maintained though the first spring is shortened and fails, and automatic control over the valve is easy to achieve.