The Al doping effects on high-frequency magneto-electric properties of Zn1 - x - yAlxCoyO (x = 0-10.65 at%) thin films were systematically studied. In the current work, the Zn1 - x - yAlxCoyO thin films were deposited by magnetron co-sputtering onto quartz substrates. The magneto-impedance spectra of the thin films were measured by an impedance analyzer. Among all the doped films studied, the thin film with 6.03 at.% Al-doping showed the highest ac conductivity and relaxation frequency. To characterize the relaxation mechanism underlying the magneto-electric properties, a Cole-Cole impedance model was applied to analyze the impedance spectra. The analyzed result showed that the magneto-impedance of the Zn1 - x - yAlxCoyO is contributed by multiple processes of magnetization dynamics and dielectric relaxation. The results imply that Zn1 - x - yAlxCoyO may be applicable for high-frequency magneto-electric devices. (C) 2011 Elsevier B.V. All rights reserved.