To illustrate how firms and customers co-create value in business to business (B2B) e-commerce, an integrated value co-creation model is proposed based on information systems (IS) application capabilities from the relational view. IS application capabilities, relational assets, customer agility and relational value are constructed and tested by empirical analysis. The empirical research tests and verifies the mediating effect of customer agility, and the interactions of IS application capabilities and relational assets, as well as their effect on relational value. This model expands the research framework of value co-creation in service dominant logic, and reveals the mechanism of how f'n'ms and customers co-create value in B2B e-commerce based on IS application capabilities, which provides the basis for further theory development and a practice guide.