To improve the porosity of ceramsite concrete can also improve its sound-absorbing property. In this paper, the expanded perlite, polypropylene fibers and foaming agent were added to improve the porosity of the ceramsite concrete. The results show that these three kinds of raw materials can enhance the sound absorbing properties of samples. The relations between porosity and the sound absorption in different sound frequencies through microstructure analysis were established. The study also found that the polypropylene fiber can improve the strength of materials, on the contrast, expanded perlite and foaming agent can significantly reduce the strength. The mechanisms were analyzed by SEM photos.