Abstract: The performance of the waveguide slot array antenna above the electromagnetic band-gap(EBG) structure isinvestigated.The kind of EBG is able to control the surface wave.The project of control the 21 S between the waveguide soltantenna by loading the periodic unit of EBG between the units has been lodged.It is found that the 21 S improved in thewaveguide slot array antenna through comparison.