The paper aims at B2B e-intermediary providing support service for both buyers and sellers, explores buyers loyalty information mechanism and key dimensions of switching cost, and theorizes a measurement model of buyers loyalty based on moderating role of switching cost. Then buyer loyalty formation mechanism and the moderating role of switching cost on buyer loyalty formation mechanism are empirically validated using a sampling survey of buyers and SEM (structural equation modeling) approach to test hypotheses. Finally, influential factors, influential degrees of buyer loyalty and moderating scope of switching cost are presented, providing guidance for training loyal buyers of B2B e-intermediary