Abstract: Because of its strong adaptability and flexibility, gas lift is widely used in dewatering gas recovery of water-producing gas wells or restoring production of water-flooded gas wells. However, the unloading process of gas lift is very complicated, and its unloading methods or process parameters are mostly determined by experience, especially for gas-lift dead-lift process. A mathematical model based on mass conservation and momentum conservation is established to describe the unloading process of gas-lift dead lift and the finite difference method is used to solve the model. Taking the DX180X water-flooded gas well in Kelameili gas field for example and considering nitrogen gas lift and natural gas lift, dynamic simulation is performed for unloading process of normal lift and reverse lift, the influencing factors including nitrogen and natural gas injection, and normal and reverse lift are analyzed, and the changes of wellhead pressure and downhole pressure with time during unloading process are modeled. To lower the starting pressure and reduce liquid flowback time or flowback quantity, nitrogen-injection normal lift method is recommended, which is particularly applicable in deep wells and waterflooded wells with relatively high formation pressure or in which coiled tubing and gas-lift dead-lift are needed. Case modeling and analysis could provide references for feasibility study, design and compressor selection etc. of gas-lift dead-lift process