The lifting speed of the aerial work vehicle is inversely proportional to the cross-sectional area of the piston rod of the cylinder, and directly proportional to the flow of the hydraulic oil. If the cylinder diameter is fixed, when the lifting speed of the aerial work vehicle becomes slow, the analysis should be given priority from the perspective of hydraulic oil flow. When the lifting speed of the aerial work truck slows down, many people will immediately adjust the relief valve in an attempt to increase the lifting speed of the aerial work truck by increasing the pressure of the hydraulic system. In fact, this is a very wrong approach. The relief valve is configured to prevent excessive pressure in the hydraulic system and protect the hydraulic system. It is very dangerous for the setting value of the relief valve to exceed the safety value of the hydraulic system design, and increasing the pressure of the hydraulic system cannot increase the lifting speed of the aerial work truck. Only when the hydraulic system of the aerial work truck cannot be started with load, the hydraulic system pressure should be checked. If the pressure is lower than the normal range, the overflow valve setting value can be adjusted. Therefore, when the lifting speed of the aerial work vehicle slows down, the factor of hydraulic oil flow should be given priority. Factors affecting the flow of hydraulic oil include: hydraulic pipelines, hydraulic valves (one-way stop valves, electromagnetic reversing valves, proportional control valves, overflow valves), hydraulic oil pumps, motor speed control devices, etc.