The reason why the swivel chair can lift is because there is a gas pressure bar in the lift device. The air pressure bar is a kind of elastic component that uses gas and liquid as the working medium and can function as support, buffer, brake, height adjustment and angle adjustment. The basic principle is that the interior is filled with high-pressure nitrogen gas. Because there are through holes in the piston, the gas pressure at the two ends of the piston is equal, and the cross-sectional area of the piston is different. One end is connected to the piston rod and the other end is not, under the action of gas pressure. The pressure on the small side of the cross-sectional area is the pressure of the air pressure rod. When the person sits on the lifting shaft, the lifting shaft will descend smoothly, the speed will be even, and the speed can be reduced to the lowest point. The lifting shaft will not lift the shaft. Rising back to the highest point, the gas spring can be stopped at any position in the stroke by means of the release device, and after stopping, there is a large locking force (can reach more than 10000N).