Abstract: Abstract: Traditional air charging method will result in the sudden drop of the cylinder temperature due to the SF6 vaporization heat absorption, the ice phenomenon outside the bottle body, the inflation speed decreasing, and the higher gas balance in the cylinder, which can not be inflated normally, increase the artificial cost, seriously affect the construction efficiency, and cause some SF6 utilization rate reduced. Based on automatic control theory, this paper studies an automatic inflating technology for gas insulation equipment in order to ensure the construction period and quality, control the artificial cost, and increase the gas efficiency and gas utilization rate of the gas insulation equipment. 1.Related theories and methods The results are mainly applied to automatic gas filling of substation equipment in the substation project to automate and improve construction efficiency. The overall technology includes automatic flow control, automatic temperature control, gas heating and protection. A gas insulation equipment automatic inflation technology with practicability and safety is realized. Automatic control technology is mainly through intermediate relay, solenoid valve and related induction and monitoring module to achieve low inflation and high closed control function in inflatable process. 2.Key technologies 2.1 Flow automatic control This technology connects the solenoid valve and the gas density relay through the electromagnetic relay, uses the gas density relay to monitor the pressure of the gas chamber and sends out the high and low signal, and automatically starts and stops the solenoid valve through the control module, so as to control the inflatable opening and closing by using the function of "low position supplementing and high stop". The flow automatic control schematic diagram, P1 and P2 are the low voltage critical and the high voltage critical junctions of the electric contact density meter, and the JZ1 and JZ2 respectively are two intermediate relays, which are powered by the 220V power supply. The control loop is mainly composed of three parts: (1) starting circuit: composed of low voltage contact P1, normally closed contact JZ2 and electromagnetic coil, when the pressure is lower than 0.45MPa, the starting circuit is closed, and the solenoid valve is opened. (2) self retaining circuit: on the basis of the starting circuit, and the constant contact point JZ1, when the pressure is at 0.45MPa~0.52MPa, the solenoid valve is continuously opened when the contact point P1 is broken. (3) the stop loop: the high voltage contact P2 and the electromagnetic coil JZ2, when the pressure reaches 0.52MPa, the P2 closed, the stop loop work, the constant contact JZ2 quickly jump, the solenoid valve closed. 2.2 Automatic temperature control The temperature control device is used to monitor the temperature of the internal environment, set the low temperature and high temperature and send out the critical signal of high and low potential, and automatically start and stop the solenoid valve through the relay control loop. 3. Conclusion This article uses automatic control theory, increasing the gas efficiency and gas utilization rate of the gas insulation equipment. (1) automatic control design is used to automate the process of inflating equipment through the control loop. It gets rid of the artificial continuous operation and real-time monitoring, greatly reduces the labor cost, and reduces the effect of human factors on the inflating process. (2)the expansion of the control module is strong, the application flexibility is large, the critical value can be set freely and reasonably with different environment conditions, and the resources and energy are rationally used. (3) the double deck design is used to heat the main body of the cylinder and realize the effective isolation from the heating device, and it has the thermal insulation function, which ensures the safety.