The structural and magnetic properties of synthetic Gd3(Fe1-xCox)25Cr4(0≤x≤0.6) and Gd3Fe29-yCry(3.5≤y≤5.0) compounds have been investigated. The structures of all the compounds are found to belong to the A2/m space group. Increase of Cr content leads to decreasing Curie temperature, decreasing saturation magnetization and decreasing anisotropy. Substitution of Co for Fe leads to a clear contraction of the unit-cell volume, but the increase of Curie temperature. Composition dependence of saturation magnetization at 5K reaches a maximum around x=0.3. It is noteworthy that substitution of Co for Fe results in a significant change of magnetocrystalline anisotropy of the Co sublattice, and changes of the easy magnetization direction of Gd3(Fe1-xCox)25Cr4 compounds from basal plane to easy axis.