Abstract: Tianmu-1 is China’s first commercially built low orbit meteorological satellite system, equipped with the GNSS occultation sounder(GNOS-M), which is compatible with receiving reflected signals from the four major GNSS including BeiDou Navigation Satellite System(BDS), GPS, Galileo and GLONASS, as well as the Quasi-Zenith Satellite System(QZSS). This study conducts the first comprehensive evaluation of ten Tianmu-1 GPS-R/BDS-R/Galileo-R/GLONASS-R global soil moisture products. Four validation datasets are used, including the fifth generation European Centre for Medium-Range Weather Forecasts reanalysis data(ERA5), Soil Moisture and Ocean Salinity(SMOS), Soil Moisture Active and Passive Observations(SMAP), and Cyclone Global Navigation Satellite System(CYGNSS). These datasets were used as reference data for comparative verification of the soil moisture products of Tianmu-1 01～10 satellites. The Tianmu-1 L2 soil moisture products are comprehensively evaluated using four accuracy evaluation indicators (root mean square error(RMSE), Bias, correlation coefficient(CC), and unbiased root mean square error(ubRMSE)). The results show that Tianmu-1 GNOS-M GNSS-R soil moisture had good consistency with ERA5, SMOS, SMAP, and CYGNSS soil moisture products overall. When Tianmu-1 GNOS-M GPS-R/BDS-R/Galileo-R/GLONASS-R has a soil moisture range of 0～0.7 cm³/cm³, its probability density function(PDF) plot is generally consistent with the PDF plots of ERA5, SMOS, SMAP, and CYGNSS soil moisture products, showing a high degree of consistency. Among them, the consistency with SMAP and CYGNSS soil moisture products is the best; The maximum RMSE of daily soil moisture values for Tianmu-1 GNOS-M GPS-R/BDS-R/Galileo-R shall not exceed 0.3 cm³/cm³; Under different vegetation cover types, there is little difference in the retrieval performance of Tianmu-1’s four reflection signals. Overall, when the four validation datasets are used as reference data, the optimal RMSE, CC, and ubRMSE can reach 0.011 cm³/cm³, 0.001 cm³/cm³, 0.999 and 0.003 cm³/cm³, respectively. Tianmu-1 GNOS-M GPS-R/BDS-R/Galileo-R/GLONASS-R soil moisture has the best agreement with SMAP and CYGNSS soil moisture products, followed by SMOS-SA (ascending orbit) and SMOS-SD (descending orbit) soil moisture products. This validates the accuracy of Tianmu-1 GNOS-M L2 soil moisture product algorithm and demonstrates Tianmu-1’s preliminary ability to retrieve global soil moisture. This article demonstrates for the first time the feasibility of using multi-GNSS reflection signals to retrieve global soil moisture, demonstrating the advantages of multi-GNSS reflectometry applications and providing important references for further understanding and optimizing the accuracy, spatiotemporal resolution, and reliability of Tianmu-1 global soil moisture retrieval.