Aimed at the problems that the conventional channel allocation mechanism based on multi-bid auction fails to ensure the fairness for cognitive users in using spectrum, this paper proposes a new price mark algorithm based on the theory of utility in microeconomics. This new algorithm takes the effect of the requirement of users' actual bandwidth and waiting time on channel utility into account, and then prices channels equivalently taking the channel utility as a standard to maximize the efficiency of system as well as the numbers of cognitive users who can access this system. The simulation and analysis on the overall efficiency of the system and other key technologies of the systems are carried out by using this algorithm and the traditional algorithm out. The results show that the algorithm can not only get good system efficiency in the case that spectrum resource is sufficient, but also can greatly improve the probability of the disadvantaged users to obtain spectrum resources with good system efficiency, and can improve the system fairness in spectrum resource scarcity.