Based on linear relationship between L band brightness temperature and L band backscattering coefficient, a time-series method is proposed to disaggregate brightness temperature at coarse resolution. The algorithm was validated with both in situ PALS dataset from SMEX02 and simulated dataset based on PALS observation. It was found that accuracy of brightness temperature for V polarization (RMSE equal 5.2K) is better than for H polarization (RMSE equal 10.03K). The results reveal a potential possibility that the disaggregated brightness temperature could be used for soil moisture retrieval.