Abstract: In order to improve the current-carrying capacity of superconducting thin films,YBa₂Cu₃O_7-σ thin films were prepared on 1-5 layer(100) oriented cerium oxide buffer films by MOCVD.Effects of buffer layers on the phase composition,crystallinity,in-plane orientation,microstructure,and superconductivity of YBa₂Cu₃O_7-σ films were investigated.Results show that YBCO films grow in a high(001) orientation with buffer layers number being 1-2 and grow in a high(110) orientation with buffer layers number being 4-5.The crystallinity and in-plane orientation of YBCO film are the best with buffer layers number being 1,with FWHM values of ω and Ф scanning curves being 2.63°and 5.21°,respectively.The crystallinity and in-plane orientation of YBCO films become worse with the increase of buffer layers.Epitaxial growth relationship between cerium oxide buffer layer and YBCO film is YBCO001//Ce O₂ 100 and YBCO010//CeO₂011.The surface of YBCO film with 1 buffer layer is mainly composed of a large area of c-axis grain,the thickness is 485 nm,the deposition rate is 4.85μ m/h,and the critical current is 20.8 A at liquid nitrogen temperature(77 K),which is higher than that of the superconducting film without buffer layer.