Abstract: In order to reduce the high temperature damage caused by atmospheric friction, aircraft radar antenna will generally be equipped with radome or dielectric window. In this paper, the bandgap characteristic of the electromagnetic bandgap (EBG) structure and the bandwidth and the good matching characteristics of the ladder-type microstrip antenna are combined to design an EBG structure ladder-type microstrip antenna with dielectric window, and then the antenna radiation characteristics and the effect of dielectric window on them are calculated and analyzed. The results show that the bandgap produced by the EBG structure can restrict the propagation of the surface wave of the antenna and improve the bandwidth and gain performance of the antenna. The structure can also reduce the mutual coupling effect between the antenna and the dielectric window, which can provide a theoretical reference for the design and application of the EBG structure ladder-type microstrip antenna with dielectric window.