Bi5Ti3Fe1-xCoxO15(x = 0,0.25,0.5,0.75,1.0)powders were prepared by a solid-state reaction.Results show that the main phases are four-layer structure of Bi5Ti3FeO15 when x ≤ 0.5,and the main phases change to three-layer structure of Bi4Ti3O12 when x ≥ 0.75.All samples have ferromagnetic properties.The sample with x = 0.25 holds the highest ferromagnetic property and its particles have homolamellar grains overlapping one another with thickness of about 5 micrometer.Its saturated magnetization reaches 0.4142 emu/g,which is much higher than that of the un-doped sample(0.0540 emu/g).