Drought is a recurring phenomenon and increasingly become a critical constraint to the sustainable development of social economy.Due to the complexity of drought, there is no a common drought index so far. Therefore, it become a hot and key to contruct an appropriate composite drought index in the study site.Taking Luanhe river basin as study object and selecting 1960 to 1979 as study period, the paper calculated relative soil moisture index based on the simulated daily soil moisture and obtained the relative soil moisture by using VIC model, and built a new composite drought index (CDI) based on the Principal Component Analysis(PCA).After evaluating the drought situation in Luanhe River basin, the monthly CDI was compared with the Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI) respectively to test the feasibility of newly proposed.The result revealed that the CDI based on VIC can better evaluate the historic dry situation in Luanhe river basin. Theresult can not only provide theory and practical value for the improvement of drought monitoring and assessment in Haihe River basin but also has reference for the evaluation in other river basins.