A strain gradient dependent crystal plasticity approach is adopted to model the size effect in the microforming process of sheet metal. To take into account the grain size effect in the simulation, the total slip resistance in each active system was assumed to be due to a mixed population of forest obstacles arising from both statistically stored and geometrically necessary dislocations. The non-local crystal plasticity has been established by directly incorporating the above slip resistance into the conventional rate-dependent crystal plasticity and implemented into the Abaqus/Standard FE platform by developing the user subroutine UMAT. The formulation has been recapitulated and followed by presentation of the numerical examples employing both the local and non-local formulation. The comparison of the counterpart simulation results reveals the grain size effect in the microforming process and demonstrates the availability of the code developed.