To dynamically adjust the bandwidth price according to the change of channel quality so as to change the users' profit, an improved spectrum sharing model considering user's mobility was proposed．The improved model comprehensively considers the impact on the price of the offered bands by all secondary users' bandwidth requirement and channel quality; at the same time, the requested bandwidth gets constrained by price, and thus users' profit change with position. The simulation results indicate that users can gain maximum profit by choosing a optimal position in the moving process.