An electrical connector includes an insulative housing and a contact module essentially composed of a plurality of contacts integrally formed within an insulator via an insert-molding process wherein the contact module is assembled to the housing via two steps along different directions perpendicular to each other. The housing forms a plurality of protrusions engaged with the corresponding ribs of contact module in the vertical direction so as to retain the contact module to the housing reliably. All the insulator, the contacts and the housing are arranged in a staggered manner.