A computer-implemented simulation method for use in a molding process by a computer process is disclosed. The method includes steps of specifying a simulating domain comprising a mold cavity and a barrel of an injection machine, wherein the barrel is configured to connect to the mold cavity; creating at least one mesh by dividing at least part of the simulating domain; specifying boundary conditions of the mesh by taking into consideration at least one motion of a screw in the barrel; and simulating a first injection-molding process of a molding material by using the boundary conditions to generate a plurality of molding conditions.