Using the WRF (Weather Research and Forecasting) model, a comparative study of simulation effects of two land surface schemes, namely SLAB (five-layer thermal diffusion scheme) and Noah (Noah land surface scheme), is conducted on one case of land fog and one case of sea fog including both offshore fog area and fog area in open seas. The results are as follows. 1) The performances of the SLAB scheme and Noah scheme in the simulation of fog in open seas are basically the same, but only the former successfully reproduces the land fog and offshore fog. 2) For land fog, compared with the SLAB scheme, the Noah scheme fails due to the surface relative humidity being 20％ lower, which is jointly caused by the stronger surface vertical heat flux resulting from the higher simulated ground temperature during the daytime and the weaker vertical water vapor flux as well. 3) For sea fog, the difference between the ground temperature and the surface vertical water vapor flux simulated by the two schemes directly leads to the difference between the air temperature at 2 m and water vapor mixing ratio, which in turn affects the intensity of the surface low pressure system and water vapor advection in Bohai Sea. As a result, their simulation performances of the fog area near Bohai Sea are quite different. In this case, the Noah scheme, which is widely used and has a comprehensive land surface process, does not perform as well as the simple SLAB scheme for land fog simulation. This article gives a preliminary explanation, but the reasons need to be further explored.