Product innovation is the springhead for enterprises to obtain and sustain competitive advantage under high uncertainty and severe competition. Product innovation network is the strategic organization form for enterprises to develop product innovation through sharing and integration of property-based resources and knowledge-based resources of enterprises. One key factor for improving the network performance is the extent of knowledge-based resources exchange, sharing and innovation. The mutual benefit of free will is the base and precondition for knowledge communication and sharing whereas process equity and trust are the conditions for enterprises' free will in the network. At the same time, trust is an important governing structure for product innovation network; reputation and long-term strategic requirement will reduce the cost of cooperation among enterprises in product innovation network.