A Synthetic Aperture Radars (SAR) is expected to observe soil moisture with high spatial resolution in large area. Recently, some multi-polarization SAR have been in operation. The purpose of this study is to develop the algorithm to estimate soil moisture by using multipolarization data acquired with the Phased Array type Lband Synthetic Aperture Radar (PALSAR) onboard the Advanced Land Observing Satellite (ALOS). In this study, we developed an algorithm for soil moisture estimation in the experimental field in Cambodia and showed that this algorithm can be potentially used to obtain the spatial pattern of soil moisture distribution with a 10 m spacing.