Electronic properties in δ-doped La:SrTiO₃ superlattices varying with the doping dimensionality and concentration are systematically studied through using first-principles calculation. The superlattices consist of periodically repeated La-doped single SrTiO₃ layers in SrTiO₃ film, and the doping dimensionality can be tuned by varying the space of the neighboring doped layers. At 25% doping concentration, the spacing between SrTiO₃ layers increases from 1 unit-cell layer to 5 unit-cell layers, i.e. the doping dimensionality changes three dimensions to two dimensions, the superlattice charater changes from metallic character into insulating character, and the charge sequence, spin sequence and orbital sequence are present in a localized state. This metal-insulator transition is ascribed to the stronger correlation effect in the two-dimensional electron system. With the two-dimensional doping concentration increasing to 50%, the correlation effect becomes weak and the system becomes metallic.