Direct simulation of 3D MHD flows in a duct with flow channel insert (FCI) relevant to R&D of fusion blanket has been conducted based on an electrical potential formula by using a consistent and conservative scheme. Comparison study of the pressure and velocity distributions of liquid metal in a poloidal duct with FCI, which has pressure equalization slot (PES) and pressure equalization holes (PEHs) with the same total area at the corresponding walls, is conducted. Both the PES and the PEHs have two kinds of locations, either in a Hartmann wall or in a side wall. 3D pressure and velocity distributions of the different cases have been given.