The invention relates to a fabricated foundation pit supporting structure which is formed by assembling of prefabricated steel concrete piles and prefabricated box-type members. The fabricated foundation pit supporting structure is characterized in that each prefabricated member is assembled by transverse joints and vertical joints and then reinforced through bolts; after fabricating, reserved leakage proof grouting holes at the prefabricated member joints are subjected to compact grouting; and meanwhile, the reserved leakage proof grouting holes in a wall are subjected to wall bottom compact grouting to fill contacting gaps of the wall bottom, and accordingly the overall foundation pit supporting structure simultaneously having overall structure rigidity and leakage preventing performance is formed.