For the input coupling and output coupling issues of compliant mechanisms with multiple degrees of freedom, a method for topological design of fully decoupled compliant mechanisms with multiple materials is presented. The multiple materials interpolation model based on the element stacking method is adopted. The maximization of the weighted sum of multiple output displacements is applied as the objective function. Both input coupling and output coupling constraints are proposed to suppress the coupling issues. The coupling constraints and the structural volume for each material are used as the constraints. The model for topological design of fully decoupled compliant mechanisms with multiple degrees of freedom using multiple materials is established. The method of moving asymptotes is adopted to solve the topology optimization problem. The obtained compliant mechanisms considering the coupling issue is different from those without considering the coupling issue. Both input coupling and output coupling of compliant mechanisms with multiple degrees of freedom can be suppressed effectively. The input and output motions of the compliant mechanisms can be completely decoupled. The influence of different coupling coefficients on the results is analyzed