The reheat steam temperature control system has the problems of multivariable control, difficult control, and so on. In order to solve the problems, a fast calculation method of multivariable control for reheat steam temperature was proposed,which was based on Smith control method and Predictive Functional Control (PFC) method. First of all, the reheat steam temperature multivariable control system was decomposed into three single-variable control systems. In every single-variable control system, the other two control volumes were taken as the interference terms. Secondly, according to Smith control idea, every single-variable control system was designed. Finally, on the basis of improving the performance index of the predictive functional control, three single-variable control systems were considered synthetically to realize the reheat steam temperature control. The simulation results of reheat steam temperature control show that with less parameters and explicit physical meaning, the proposed method is about 50 times as fast as the traditional predictive control with constraint conditions. The experimental results show that the proposed algorithm can effectively improve the quality of the reheat steam temperature control in the field.