GaFeO₃ is one of the most promising ferromagnetic materials due to its magnetoelectric coupling effect. GaFe_1-xCo_xO₃ (x=0, 0.02, 0.05, 0.07, 0.10) ceramics were prepared by the conventional solid-state method, and the effect of Co substitution on the microstructure, electrical leakage and magnetic properties was investigated. The XRD patterns and Rietveld refinement using the FullProf package showed that the secondary phase with a Fd3¯m space group was present in addition to the main GFO phase with a Pc2₁n space group, and with an increase of Co doping, the proportion of the secondary phase and the lattice distortion increased. The leakage current density of the GFCO-x samples decreased by approximately 7 orders of magnitude for Co=2at%. The improved magnetization in GFCO ceramics was attributed to the secondary phase and enhanced lattice distortion. This work suggests that the magnetism was improved by doping Co and the leakage current would be decreased sharply without prominent fluctuation of T_C in the meantime by the incorporation of trace amounts of Co.