Global Positioning System Interferometric Reflectance (GPS-IR) is a new remote sensing technique, which can be used to estimate soil moisture content near the surface. From the view of multi-satellite fusion, an estimating method of surface soil water content based on multi-satellite fusion is proposed. Firstly, the direct and reflected signals of multiple satellites are separated by low order polynomial fitting, and then the sinusoidal fitting model of the reflected signals is established to obtain the relative delay phase. Secondly, the multiple linear regression inversion model of soil moisture is established, and the input variable set of the model is determined by the correlation coefficient of each satellite. Finally, the advantage of multi-satellite fusion is brought into full play to retrieve soil moisture. The feasibility and effectiveness of single satellite and multiple satellite fusion inversion are compared and analyzed through the monitoring data provided by the Plate Boundary Observation (PBO). The experimental results show that the multiple linear regression model can realize the effective fusion of multiple satellites. Compared with the single satellite, the inversion accuracy is higher and the inversion error is more stable.