X-ray diffraction patterns and thermomagnetic curves show that all compounds are almost of single phase.All ErFe11-xCoxTi compounds (x=0—11) crystallize in the ThMn12-type structure.Substitution of Co for Fe leads to an increase of Curie temperature and a monotonic decrease of lattice constants.The composition dependence of saturation moments exhibits a maximum at about x=3. The easy magnetization direction (EMD) at room temperature,for x≤4, is along the c-axis, for 6≤x≤9,is perpedicular to the c-axis, while for further increasing x, it goes back to the c-axis. The interesting change of EMD of ErFe11-xCoxTi compounds may result from the preferential occupation of Co and the different contribution to the magnetocrystalline anisotropy from different transition-metal sites.For all ErFe11-xCoxTi compounds, a spin reorientation occurs below the Curie temperature.A tentative phase diagram for ErFe11-xCoxTi compounds has been given.