The 2nd Global Soil Wetness Project (GSWP2) is an ongoing environmental modeling research activity initiated by the Global Energy and Water cycle EXperiment (GEWEX). The SiBUC (Simple Biosphere including Urban Canopy) land surface scheme is one of the participants of the GSWP2. In order to estimate the global soil moisture field as accurately as possible, and to utilize the products of GSWP2 simulation more efficiently for water resources application, SiBUC is run with irrigation scheme activated. In this way, global 10-year simulation considering irrigation was implemented, and global distribution of irrigation water demand was estimated. There is obviously negative correlation between annual precipitation and irrigation water demand. However, there are some grids those have positive correlation between precipitation and irrigation. The difference of the relationship can be explained by NDVI. It is implied that the irrigation facilities in such area are not adequate.