Abstract: Ice storage cooling air conditioning systems play an important role in power grid peaking and improving the economics of cooling. In this paper, through the study of the ice storage process of coil-type ice storage system, it is found that the ice storage process contains two distinct phases: In the first phase, from 10.0 to 4.0℃, the density of water increases as the temperature decreases, and the cold water at 4.0℃ rapidly gathers at the bottom of the storage unit and gradually fills the whole water area. In the second phase, from 4.0 to 0℃, the density of water decreases as the temperature decreases. In the first stage, the ice layer first appears on the lower surface of the heat exchanger tube; in the later stage, the ice layer starts to be generated on the upper surface of the heat exchanger tube as more low-temperature water is gathered above. In this experiment, upon completion of the 100-minute ice storage process, the thickness of the ice layer on the upper and lower surfaces of the heat exchange tube reaches 8.56 mm. Afterwards, the thickness of the ice layer on the upper surface gradually exceeds that on the lower surface. This paper reveals the influence of natural convection inside the ice storage unit and the reversal of water density at 4.0℃ on the icing process, which is of guidance value to the optimal design and operation control of the coil-type ice storage system.