In order to study the photoluminescence properties of freestanding porous silicon filled with CdS nanopaticles, a freestanding porous silicon was prepared by using a p-type silicon wafer with a resistivity of 0.01~0.02Ω·cm by two step anodic oxidation method as the first step, and then CdS nanoparticles were filled into the freestanding porous silicon by the electrophoresis method. The morphology, phase structure, composition and luminescence properties of the prepared samples were characterized by scanning electron microscopy, X-ray energy spectrum analysis, X-ray diffraction analysis and photoluminescence analysis. The results show that, the CdS nanoparticles are successfully filled into the freestanding porous silicon, and CdS nanoparticles present (210) diffraction peaks. The luminescence peak of CdS nanoparticles filled freestanding porous silicon is find red-shifted from 570 nm to 740 nm. The electrophoresis time directly affects the filling amount of CdS nanoparticles, resulting in the changes of the peak intensity and the peak position.