The research aims at profit maximization, and firstly, according to the purchase methods for one-to-many purchase situation, the research installs purchase agent system model of virtual organization to solve the problems of purchase possibly faced by the virtual organization on supply chains. The research uses the results of value allocation model of virtual organization researched by AHP to install the module of value distribution agent system. In the last step, the research uses the joint procurement cycle and quantity estimation model made by back-propagation neural network algorism to install the model of enterprise demand estimation agent system and the model joint procurement agent. The goal aims at construction of the optimal solutions and methods to the negotiation between buyers, the joint procurement between the raw material suppliers, the item purchase assignment of jointly the goods with various shoppers, distribution of the purchase goods and so on.