Abstract: Abstract: Soil moisture plays a major role in the water and energy budgets of continental surfaces. In the inversion of soil moisture using passive microwave remote sensing technology, soil roughness is the most critical factor restricting the accuracy of the inversion algorithm. Multi-angle remote sensing data has certain advantages in obtaining surface roughness information. Therefore, multi-angle passive microwave observation data has greater application potential in soil moisture inversion. At present, there are few studies on how to use multi-angle passive microwave data to reduce the effect of roughness on soil moisture inversion. Therefore, this study explored the application method of multi-angle passive microwave remote sensing data in soil moisture inversion by analyzing the multi-angle simulated data of soil microwave emissivity. In this study, the Advanced Integral Equation Model (AIEM) was used to simulate the multi-angle microwave radiation of the soil with different Soil Moisture Content (SMC) and roughness. The Brewster angle was calculated based on the trend of the V polarized emissivity with observation angle. The calculation results of Brewster angle showed that Brewster angles of soils with different moisture content distributed in the range of 60°-80°. Based on analysis of the simulated data, Brewster angle had a good consistency with SMC while Brewster angle was not sensitive to parameters such as soil temperature, soil bulk density, and soil roughness. The Brewster angle would change by 15° with SMC changed from 0.05 cm3/cm3 to 0.40 cm3/cm3. When the root mean square height of soil roughness increased from 0.5 cm to 3.5 cm, the Brewster angle value increased with the increase of roughness, but the maximum change in angle did not exceed 2°. When the bulk density of the soil changed from 0.9 g/cm3 to 1.4 g/cm3, the Brewster angle value increased by no more than 1°. The soil temperature changed from 10 ℃ to 35 ℃, and the Brewster angle changed with the increase of soil temperature. When the root mean square height of the soil roughness and the soil bulk density were combined with different values, the maximum change of Brewster angle did not exceed 2°. This showed that the total influence of soil roughness and soil bulk density on Brewster angle had no obvious accumulation of errors. This study presented an algorithm for inversion of SMC by using the Brewster angle information of soil microwave radiation. Through the analysis of simulated data, a good linear relationship between the tangent value of Brewster angle and SMC was found. The regression results based on simulated data showed that the coefficient of linear fitness between the tangent of Brewster angle and SMC was 0.94, and the root mean square error was 0.027 cm3/cm3. The verification results based on simulated data showed that the coefficient of determination between predicted value of SMC and theoretical value was 0.95, and the root mean square error was 0.024 cm3/cm3. The inversion algorithm proposed here had robust characteristics for different types of soil roughness autocorrelation functions. The prediction accuracy of the algorithm for SMC was little affected by the roughness autocorrelation functions. For different types of roughness autocorrelation functions, the root mean square error between the predicted value of SMC and the theoretical value was 0.023-0.027 cm3/cm3. The SMC inversion algorithm based on Brewster angle utilized the relative change of multi-angle soil emissivity rather than its absolute value and this research provided a novel research idea for the inversion of SMC by using multi-angle passive microwave remote sensing data.