In this paper, by using the percolation theory and considering both global and local information, the minimal resource utilization scale of animals are obtained by analyzing spatial distribution patterns of the resource. The spatial distribution pattern of resource are not so important when resource concentration is so high that it could completely meet the requirements of maintaining the existence of animals. But when the efficient degree of resource is low, the distribution of grazing animals is influenced by the spatial pattern of resource to the great extend. The higher the resource concentration is, the greater the resource utilization scale becomes. So that, according to tile resource concentration, resource utilization scale and efficiency, the composition of a livestock could been optimized in order to increase the total resource utilization efficiency. This is essentials of optimizing composition of livestock.