Soil moisture is one of the key factors to control the distribution of latent and sensible heat flux at the interface of land surface and atmosphere, which can have impacts both on weather and climate processes on various temporal and spatial scales, because of its certain memory properties. In the numerical model, the uncertainty of soil hydraulic parameters is one of the main reasons for the uncertainty of soil moisture simulations. Based on the Yin He Global Spectral Model (YHGSM), this paper introduces the VG (van Genuchten) soil water retention curve model, and discusses the influence of two different sets of soil hydraulic parameters on the offline simulation of soil moisture and the global medium-range numerical weather forecast. The soil type information needed for soil hydraulic parameters comes from the Global Soil Dataset for ESMs (GSDE). The offline results show that, except for the large simulation deviation of permafrost and organic soil, the land surface module of YHGSM has a good ability to simulate soil moisture in most parts of the world, and the simulation accuracy is similar to that of ERA5 soil moisture reanalysis products. Soil hydraulic parameters have a certain influence on soil moisture, and that the influence strength is closely related to soil types and local climatic conditions, and coarse structure soil is more sensitive to model parameters. The results of the global medium-range numerical forecast experiments indicate that, by changing the soil moisture, soil hydraulic parameters not only have impacts on the short-term forecasting of near surface temperature and humidity, but also lead to significant changes in the large-scale circulation after 6-days forecast. Therefore, for the global medium-range numerical forecasting system, it is very important to optimize soil hydraulic parameters and improve the ability of soil moisture simulation.