The energy usage of building has occupied the large portion of total energy consumption. It is important to develop the building energy consumption minimization method. The new study adopted the thermal conservation equation for this multivariable control issue and the linear matrix inequality based on linear quadratic regulator for mixed H2&H∞ control. After substituting the obtained control gains into the original thermal systems, the asymptotically stabilities of whole systems are guaranteed. The comparison between the traditional and current control scheme are made.