Under the background of global warming, it is possible to open the Arctic summer route and even to conduct commercial utilization. The Arctic sea fog would seriously affect the navigation safety of ships along the channel. The existence of sea ice makes the interaction between sea and air very complicated, which is a problem that cannot be ignored in the study of Arctic sea fog. Ship-based observations show that unlike the common mid-latitude advection cooling fog whose formation sees the rate of surface air temperature drop generally greater than that of sea water temperature drop, the Arctic sea fog occurs when the rate of sea water temperature drop exceeds that of surface air temperature drop because of sea ice. However, it remains a doubt whether or not the distribution of sea ice would affect the accuracy of the model simulation of sea fog. In this paper, Polar Weather Research and Forecasting (Polar WRF) model is used to simulate a sea fog case observed during China's seventh expedition to Arctic in summer and sensitivity experiments on sea ice fraction are conducted. The experiments are verified by ship-based observations and the reanalysis data of European Centre for Medium-Range Weather Forecasts. The results show that in areas of low floating ice fraction (sea ice fraction lower than 50%), when considering distribution features of sea ice, Polar WRF model can more accurately describe latent heat flux and upward water vapor flux and simulate the process of surface air temperature drop and humidification and the change of relative humidity. Therefore, Polar WRF model with sea ice fraction can better describe the three-dimensional structure and the evolution of Arctic sea fog.