Integrating optimization techniques with GIS has recently been a rapid expansion of interests and researches in the area of spatial decision support (SDS) and resource allocation. Land use planning or allocation (LUP or LUA), as one of main resource allocation issues, refers to the optimal allocation of multiple sites of different land uses to an area, which not only relates to the conditions and quantity of land, but also should consider the spatial relation of sites and other influences. Recent developments in this field focus on the design of allocation plans that utilize mathematical optimization techniques. In this paper, we firstly describe LUP with mathematics and formulate a multi-objectives optimization model for it, and then demonstrate how genetic algorithm (GA) can be used to solve this nonlinear and multi-objectives spatial optimization problem. The objectives of optimization model consider both planning cost and spatial pattern of the land use. The method is applied to a case study in China.