The method is an extension of the adaptive mesh refinement procedure, originally developed for hyperbolic conservation laws, to the space-time staggered FDTD scheme in 2D. The algorithm allows for local space-time mesh refinement in electromagnetic simulations based on FDTD method. A second order accurate formulation based on high order interpolations, and enforced conservation of the magnetic field circulation at the fine-coarse grid boundaries is constructed. The new algorithm is stable and accurate for long time integration. We applied it to simulate an optical ring microcavity resonator using multi-level grid refinement.