Abstract: We address the problem of spectrum sharing in cognitive radio networks where multiple primary service providers compete with each other to offer spectrum access opportunities to the secondary users.We formulate this problem as an oligopoly market competition and present spectrum trading model of the oligopoly market,each of the primary service providers aim to maximize its profit under quality of service(QoS) constraint for primary service.For the secondary service,we adopt a utility function to obtain the inverse demand function.We present distributed algorithms to obtain the solution for the dynamic game.The numerical results reveal the solution convergence to the Nash equilibrium.