A screw foundation system for aligning and fastening a rod- or post-like object in the ground includes a sleeve-like plastic receiving part which can be screwed into the ground and which, in the fastened state, accommodates an end region of the rod- or post-like, object and surrounds their periphery of the object with a distance at least in certain portions; and a curable filling compound which, in the fastened state, fills the space between the end region of the rod- or post-like object and the inner contour of the receiving part, wherein the inner contour has undercuts for anchoring the cured filling compound. The screw foundation system can include a screwing-in tool having a dimensionally stable fitting core which can be inserted into the receiving part in order to screw in the latter.