Soil moisture (SM) is an important parameter for drought monitoring as well as soil erosion, crop production and surface temperature. Microwave remote sensing especially at L-band is one of the most promising approaches to monitor the variable of SM at the global scale with frequent revisiting times. We carried out a large number of experimental and theoretical studies to assess the potential of monitoring soil moisture by means of both active and passive microwave satellite observations. Improving the inversion accuracy of soil moisture by combining active and passive microwave remote sensing data is an important task for the development of quantitative remote sensing. In this paper, the main objective was to estimate soil volumetric water content (SVWC) of bare soil collaborative using the active and passive observations. A novel approach, which was based on the simulation database of the advanced integral equation model (AIEM), was presented. In the method, we took the advantages of the active and passive microwave remote sensing data to obtain SVWC. Based on the analysis of the simulation database, some significant patterns had been found that the characteristics of the vertical polarization microwave emissivity (EV) had stronger sensitivity to the soil moisture than the roughness while the active microwave backscatter coefficient was more sensitive to the soil roughness than passive microwave. Among the vertical polarization microwave emissivity (EV), horizontal polarization microwave emissivity (EH) and VV backscatter coefficient (σvv),the effect of roughness on theσvv was greater than on passive microwave surface emissivity (EV and EH) and the effect of roughness onEV was minimized. TheEV and theσvv were used to estimate the soil surface roughness, and on the premise of knowing soil surface roughness, soil moisture can be accurately calculated by passive microwave data. This algorithm had following two steps, the first step was to estimate the soil surface roughness using the vertical polarization emissivity and VV polarization backscatter coefficient; and the second step was to estimate SVWC using a combination of theEV andEH at L band under the condition of soil roughness was known. At last, based on the dataset of the SMAP experimental campaigns carried out in 2012 (SMAPVEX12), we evaluated the superiority of the algorithm. The validation data were obtained through the online Data Pool at the National Snow and Ice Data Center of the SMAPVEX12, the good inversion results were achieved withR2 equal to 0.6637 and the RMSE equal to 0.0607 cm3/cm3. One of the biggest advantages of the algorithm developed in this paper was that the coefficient of algorithm was calculated by the simulated data set, which different from the conventional experience algorithm that depended on the field data, which reduced greatly the limitations of the algorithm in practical application. The threshold value 0.25 of NDVI was used to select the appropriate sampling points for validation and the error of the result partly came from the effect of the little vegetation covering the surface, so the algorithm proposed in this paper should be revalidated using the observed data of the bare soil in the future.%土壤水分是进行干旱监测、土壤侵蚀、农作物产量预测以及地表温度研究的重要参量，利用主被动微波协同的方法提高土壤水分的反演精度是定量遥感发展所面临的重要任务。本文基于土壤L波段微波散射辐射模拟数据集，通过对比分析主被动微波数据对土壤水分含量和粗糙度2个参数的敏感性，提出了基于L波段主被动协同的裸土土壤水分反演算法，算法充分利用了被动微波地表发射率对土壤水分较为敏感，而主动微波后向散射系数对地表粗糙度较为敏感的特点。首先由地表垂直极化发射率和 VV 极化后向散射系数协同提取地表粗糙度信息，再由被动微波双极化数据结合地表粗糙度信息来估算土壤水分信息。利用SMAPVEX12实验数据集中部分稀疏植被采样点的观测数据对算法进行验证，验证结果显示，土壤水分反演结果与地面实测数据相关性为0.6637，RMSE为0.0607 cm3/cm3。该文反演算法模型系数直接由模拟数据集计算得到，克服了常规经验算法的发展对地表实测数据的依赖性，减小了算法在实际应用中的局限性。
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