Understanding the multiphysics inside the catalyst layer of polymer electrolyte fuel cell (PEFC) is critical to design of optimized catalyst layer porous structure. Pore-scale simulation directly computes detailed multiphysics phenomena occurring inside the heterogeneous structure, which is therefore a promising tool in improving the understanding. However, for the wide-spread use of pore-scale simulation, its computational cost needs to be further reduced. In this work, the multiscale method is applied to multiphase pore-scale simulation of the cathode catalyst layer. Simulation results show that the computational cost of multiphase pore-scale simulation is substantially decreased by the multiscale method without sacrificing the accuracy.