The agility of supply chain as well as the competitiveness of the knowledge service network system is affected by knowledge sharing efficiency. In this paper, an evaluation index system for the knowledge sharing efficiency of the knowledge service network system in agile supply chain was constructed in terms of knowledge system, knowledge sharing environment, coordinating actions and sharing results. After evaluation indexes were reduced with rough set theory, a knowledge sharing efficiency evaluation model for the knowledge service network system in agile supply chain was established with error back propagation (BP) artificial neural network, and the network model was simulated with sample data, proving the evaluation result could comprehensively, accurately reflect the actual situation. Thus, the model possesses a very broad application prospect.