By adopting the principle of kinematic inversion and the mathematical tools such as rotation matrix,the general analytic formula of cam contour of flat evolution type of high-speed printing press mechanism from German is obtained through deduction. The study and discussion surrounding the different values of the angle σ between flat and connecting rod are carried out,the problem of cam contour design of flat evolution type mechanism of is solved successfully,the important theoretical basis for further popularization and application of this evolution type is provided.