The energy storage technology can be applied for the efficient use of energy, to solve the problem when the source of renewable energy is unstable and the insufficient supply or oversupply caused by peaks and valleys in the power supply network.In view of the energy storage system, the development of adiabatic compressed air energy storage system (ACAES) is rapid. Although the trigenerative ACAES including power output, cooling and heating processes have been studied extensively, the research on discharging process of ACAES is still in lack. In this consideration, this paper studies the influence of key factors in the discharging process on the system performance, and the expansion stage and water mass flow rate of heat exchanger are considered. In the system simulation. the number of expansion stages is set as 2, 3, 4, 5 and 6. And the range of water flow rate is selected from 1 kg·s-1 to 6 kg·s-1. On this basis, the following four aspects of performance are analysed: charging and discharging time, power and energy supply, efficiency, and exergy loss. Simulation results indicate that quantities related to the charging process keep constant. With enhancing heat exchange, energy distribution will be changed. And the enhanced heat transfer is suitable for a longer discharging time and less cooling capacity. But the enhancement of heat transfer is limited. As the increasing expansion stages will weaken the output power and cooling supply, the optimal expansion stages should be chosen with the help of efficiency analysis. This paper provides a reference for the practical optimisation of discharging process of ACAES.