Al (1%wtSi)/Zr multilayers were fabricated by DC sputtering techniques on doped fluoride glass substrates for 17~19 nm extreme ultraviolet radiation. The surface roughness of the multilayers with variable layer pairs (N=10, 40, 60 and 80) were measured by an atomic force microscopy. Their reflectivities were measured and fitted based on multilayer growing method improved by Stearns. Experiment and analysis present that the interface roughness were variable with the growing of Al/Zr multilayers and coincide the Stearns′ method as N≤40.