Adequacy is a crucial consideration in the planning and operation dispatching of the power system, especially in the power system with high penetration of renewable energy sources. Considering the multi-time scale characteristics of renewable energy power and the response characteristics of flexible regulation resources, a multi-time scale adequacy evaluation method based on empirical mode decomposition is proposed. In this method, a net load curve is decomposed into multiple component curves at a multi-time scale by the empirical mode decomposition (EMD) algorithm. As a result, the adequacy demand of the system at each time scale is obtained by waveform recognition. Moreover, the available adequacy resources of the system at different time scales are obtained according to the regulation models of flexible regulation resources. By analyzing the adequacy demand and available adequacy resources of the system at the same time scale, the adequacy evaluation indices at each time scale can be calculated and weighted to form the comprehensive indices. At last, taking a practical power system as a case, the adequacy evaluation indices at each time scale with different capacities of renewable energy sources and energy storage systems are compared and analyzed. Simulation results indicate the validity of the method.