As an important variable of the climate system, soil moisture (SM) plays a key role in the surface runoff, evapotranspiration, energy balance, and carbon cycle. And its heterogeneity and variability in space and time bring in continuous influences on the simulation and prediction of atmospheric circulation, surface processes, and land-atmosphere interactions (Fan et al., 2020;Schwingshackl et al., 2017;S. I. Seneviratne et al., 2010). SM is also a key variable in surface water fluxes and is critical for drought monitoring and assessment (Velpuri et al., 2016).Compared with other climate variables (e.g., precipitation and temperature), the measure of SM is more difficult and complicated. Moreover, due to the sparse distribution of gauge observation, the spatiotemporal coverage and representation are not well obtained. Thus, it prevents us from conducting reliable quantitative analysis and comprehensive studies. With the rapid development of remote sensing technology and the continuous improvement of relevant models, various SM estimation products (such as reanalysis, Land Data Assimilation Systems [LDAS], and satellite retrieval) are more widely used in the existing research because of their good spatiotemporal continuity. But due to the differences in data source, algorithms, coverage, and spatiotemporal resolution, all these products are subject to great uncertainties Chen et al., , 2021. On the other hand, many different products (e.g., ERA-Interim and ERA5) are constantly being iterated and updated. Therefore, effective evaluation of SM products is a prerequisite for more appropriate and targeted use of SM products in different regions and time scales. And it also provides scientific support for the application of SM products in hydrological research and drought monitoring (Chen &