The soil moisture and precipitation data of Inner Mongolia of CMA Land Data Assimilation System (CLDAS) were evaluated. The drought that happened in Inner Mongolia in the summer of 2014 was analyzed using CLDAS with RSM and DNP, and the results of dry year (2014) and wet year (2013) were compared with SPI and PDECI. The analysis results revealed that the dynamic variation of daily soil relative moisture and the precipitation area and grade can be reconstructed by CLDAS, which can meet the requirements of drought monitoring. The soil relative moisture index based on CLDAS can monitor the daily and regional changes of drought of quickly and conveniently. The continuous absence of effective precipitation day is relatively valid for estimating longperiod and continuous drought. In brief, CLDAS is able to fulfill the timeliness, resolution and representativeness requirements of meteorological service, and can serve research and operation widely as important supplementary for monitoring data. It is valuable for areas like Inner Mongolia where weather station is relatively scarce in a widespread area.