Standard metal gauge is a common measuring instrument in the measurement industry, which has been widely used in the measurement industry. This paper aims at the problems of low efficiency and low experimental accuracy in the manual verification process of standard metal gauge. A liquid level control method is proposed. Firstly, the standard metal gauge tank is modeled and analyzed, and the switching points of large and small flow valves are calculated. Then, the liquid level sensor is used to read the liquid level height at the glass pipe of the tank neck in real time, and the duty cycle of the small flow valve is controlled by the programmable logic controller, So as to achieve the purpose of high-precision liquid level control. Finally, based on the simulation platform, the liquid level control at the glass tube of the standard metal gauge is simulated, and the liquid level control error is ± 0.05 mm. The results show that the method proposed in this paper can improve the liquid level control accuracy of standard metal gauge and has good popularization value.