Humid air turbine (HAT) cycle is one of the most advanced gas turbine cycles. Saturator water temperature control is a control strategy that adjusts the water flow rate to keep the outlet temperature at the designed value. A HAT cycle model based on the HAT cycle test rig of Shanghai Jiao Tong University is built to analyze the influence of water temperature control on both steady-state and dynamic performance of HAT cycle system. The simulation results show that system efficiency increases by 0.071% for the study object on 75% load. The dynamic response of output power changes little, while the saturator can achieve stable faster.