Thin films of PbTiO₃ (PT) and (Pb, La)TiO₃ (PLT) were grown at 600^oC on (100)MgO substrates by rf-magnetron sputtering. The crystal orientation of the PT thin films was investigated with various cooling rates (8^oC/min to 33^oC/min). It is found that the degree of c-axis orientation of the PT thin films increases with increasing cooling rates and the degree of a-axis orientation increases with decreasing cooling rates. While, c-axis orientation of the PLT thin films is grown independent of the cooling rates. The cooling rates are essential for the control of the orientation of the PT thin films on (100)MgO substrates.