The mathematical model of mechanism problems can be translated a multi-variables non-linear equations

and the initial value is needed for solving the equations

it is a difficult problem to give the initial value for the no-linear equations.The homology continuation algorithm has resolved this difficult problem without given initial value and can find all solution

but a special programming is compiled at the same time.A numerical solution of new general homology function and homology continuation algorithm is put forward and combining with Maple10.0 toolbox.The study for solving the problem of planar four-linkage is carried out by using this method

and all solutions are obtained.A simple realization method for homology continuation method and more selection scheme for mechanism design is provided.