The numerical modeling of the ice formation in the ballast tank of polar ships has been established by adopting the volume of fluid (VOF) model in FLUENT to simulate the liquid phase and vapor phase, in order to analyze the influences of low temperature environment and ballast water capacity on the ice formation, and the heat transfer mode of the ballast tank of polar ships. The variations of the ice field in the computational domain with set-ups of different temperature environment and ballast water capacity are observed to analyze the influences of various factors and conditions on the ice formation in the ballast tank. It is found that the ice grows along the bulkhead to form a uniform ice layer, then grows transversely and vertically to form an ice layer completely covering the water surface, and finally grows downward along the bulkhead on the other side to form an arch shape as a whole. It is also observed that for the same ballast water capacity, the lower the ambient temperature, the faster the icing rate and the higher the icing degree; while for the different ballast water capacity, the lower the free surface, the better the effect of the hot air in the tank and the slower the icing rate. It can be concluded that the icing law of the ballast tank under low temperature is revealed through the numerical simulation of the ice formation of the polar ship ballast tank under low temperature. It can provide references for the deicing and winterization measures of the polar ship ballast tank.