Cold ring rolling is a much complex physical process with multi-factors. Two forming parameters, the feed rate of mandrel and the rotational speed of main roll, affect the quality of deformed ring significantly and the feed amount per revolution of ring in the form of their ratio. By their ratio, the interactive effects of the two forming parameters on the T-shaped cold ring rolling process are explored through 3D-FEM in Abaqus software. The results show: firstly the study objects (roll force, growth rate of diameter, degree of inhomogeneous deformation, filling capability of groove, average side spread and fishtail coefficient) are almost invariable if the two parameters are increased (or decreased) proportionally; secondly whether the ratio is changed by the feed rate of mandrel or by the rotational speed of main roll, the variation of each study object with the ratio is approximately the same; thirdly the increase of the ratio is beneficial to the growth of diameter and the restrictions of inhomogeneous deformation, average side spread and fishtail coefficient, but it causes the roll force to increase and the filling capability of groove to decrease.