We developed a method of real space renormalization group transformation, suitable to handle a variety of space-modulated disordered systems. By this method, maintaining the relative space-modulation structures unchanged under transformation, we could study the critical properties of Anderson localization of these systems. By solving the RG equations for disordered metallic superlattices with finite-lattice approximation, the fixed point and critical exponent have been calculated approximately. It is found that space-modulation may change the properties of electronic localization in disordered systems to some extent.