The flexibility and high reliability of cloud computing have generated a tremendous amount of economic benefits. With the growing demand for cloud resources, the task about how to making users' demand adaptive to the supply of cloud resources during peak and nonpeak hours becomes extremely challenging. However, most of the existing mechanisms mainly focus on the allocation of cloud resources, and ignore the balance between supply and demand of cloud resources. To improve the situation, this paper presents a combinatorial auction model for the cloud resource allocation and consumption shifting problem, and then puts forward a truthful auction mechanism with two different price curve functions, that is, staircase and continuous price curve. The proposed mechanism can effectively allocate and shift cloud resources to alleviate the pressure of cloud infrastructure during peak hours. Both the theoretical analysis and simulation results show that the proposed mechanism guarantees desired properties including individual rationality, budget balance, truthfulness and computational efficiency. In addition, extensive simulation results also show that continuous price curve outperforms stair case price curve in terms of system efficiency and balance efficiency.