This paper points out that the price, quality, the level of supplying on time, the level of after-sales service and so on can be regarded as resources that the suppliers can provide, and proposes a concept called the comprehensive level of resources exploitation which can be used to evaluate the comprehensive effect of order quantities allocation of one product between several suppliers. A relative index is presented to measure the comprehensive level of resources exploitation. The index is fit for comparison between several order quantities allocation plans in different time to evaluate which plan exploits the resources of suppliers more effectively. Finally, this paper establishes a linear programming model to solve the optimal order quantities allocation based on the highest comprehensive level of resources exploitation.