Abstract: With the population growth, the rapid economic development and quick expansion of cities, the intensity of land-use is increasing, and the problem of land fragmentation has grown more and more serious. On the condition that the demand of economic and social development was satisfied, a model of land use spatial structure optimization was constructed based on GIS, genetic algorithm, multi-objective decision and landscape ecology theory, which could reduce the degree of landscape fragmentation, protect the habitat of living things, and improve the efficiency and benefit of land use. The scale issues, conversion rules and algorithm flow of the model were also studied particularly in this paper. On the basis of LUPOlib1.0 software package provided by Annelie Holzkamper, etc., the secondary development of the procedure by using C/C++ language was carried out. Taking Deqing County as an example, its land use spatial structure optimization was studied by computer emulation on dynamic process. By using the optimization model, although the industrial and urban land concentration was decreased, the agglomeration degree of farmland, garden, forest and rural residential land was improved, and as a whole, the degree of land fragmentation was reduced. The results indicated that this model can be used to optimize land use spatial structure and reduce land fragmentation.