Abstract: The periodically arranged acoustical structures are commonly used in the modern architectures as they can improve the acoustical environment while decreasing the demand for the absorptive materials. In order to investigate the acoustic characteristics of the two-dimensional periodic flat surface, a simulation model of sound absorption is established. First of all, the linear system of equations of the sound absorption coefficients is theoretically deduced based on the boundary condition. Then the equations are solved by numerical analysis. Finally, experiments in both the Kundt's tube and the reverberation chamber are carried out to verify the theory. The experimental results fit the calculated curves well. It is shown that by utilizing this simulation model, a good prediction of sound absorption of the two-dimensional periodic flat surface can be obtained. Besides, data analysis shows that in the periodic structure, with the same area of the absorber, the larger the ratio of the absorber is, the higher the sound absorption coefficient will be; with the same area and the same ratio of the absorber, the longer the length of the edge is, the higher the sound absorption coefficient in the high frequency range will be; with the decrease of the length of the edge, the edge effect will decline.