In this paper the effective index perturbation technique in combination with two-dimensional(2D)/three-dimensional(3D) plane wave expansion methods is used to predict resonant mode frequencies of donor-like and acceptor-like H1 photonic crystal slab cavity, and their results are very close to the ones obtained by three-dimensional finite difference time domain method.For donor-like H1 photonic cavity,when the perturbed effective index by matching dielectric band edge is used,there is a relatively small freq...