Abstract: This paper presents an equivalent analysis method for transmission properties of periodic reactance-loaded dielectric structure.The equivalent relationship between the strip width and the cylindrical wire diameter is established through the analysis of periodic strip grid and wire grid mounted on the A-sandwich dielectric structure in 5~15 GHz frequency ranges,and the effects of the incidence direction, the position and period of grid,the wire diameter,as well as the thicknesses of dielectric layers on the equivalence are also studied.The simulation results show that the equivalent strip width for a cylindrical wire is π/2 times the wire diameter under an arbitrary incidence angle if the wire diameter is small enough.The equivalent error caused by bigger wire diameter can be revised by the experience formula of the equivalent coefficient.