Abstract: In recent years, the numerical manifold method(NMM) is a new type of numerical calculation method. The numerical manifold method includes a finite covering system that has been applied to the simulation of the plastic forming process of viscoplastic metal, using a four-node rectangular mesh as the mathematical covering mesh, taking the constant covering displacement function and the complete first-order approximation of the covering displacement function, and adopting the penalty function method for the introduction of volume invariant condition. Combined with the above, the basic solution formula of the numerical manifold method for viscoplasticity was derived and the solution of the initial velocity field and the imposition of friction boundary conditions was analyzed. Finally, MATLAB software was used for programming and simulation with specific numerical examples, and the results reflect that the numerical manifold method has good application prospects in the field of metal plasticity processing.