Aiming to facilitate a high penetration of renewable generation and the low energy consumption technologies at the demand side, there is significant development of low-carbon building Microgrids integrated with renewable generation. However, renewable generation is usually intermittent, uncertain and uncontrollable, which induces power mismatches between power demand and supply for the low-carbon building Microgrids. Therefore, a two-layer method for an office building Microgrid is proposed to smooth the tie-line power by scheduling the thermal mass of the building and the electric vehicles at two different time scales. A Vehicle-to-Building control strategy was developed to dispatch the electric vehicles as a flexible resource. Numerical studies demonstrated that the proposed method can smooth the fluctuations of the tie-line power for the office building Microgrid.