Photonic crystals have been extensively used in microwave and millimeter wave application,and that kind of photonic crystal whose structure is integrated into microstrip circuits have a good future.Microstrip structure periodically loaded with rectangular metal patches can be designed to be an excellent photonic crystal with a planar topology.Surface wave in certain frequency band will not be permitted to propagate.In this paper,Green's function plus method of moments is introduced to analyze this kind of photonic crystal.The propagation constant of surface wave for this microstrip structure is obtained by solving the characteristic equation.Proper parameters are chosen to get expected surface wave bandgap.This microstrip structure is valuable to microwave circuits and phased array antennas.