Abstract: The finite differential method based on the rigorous electromagnetic theory is used to calculate the optical absorption and reflectance on corrugated surfaces with arbitrary function profiles.To simulate the related photoacoustic (PA) angular spectroscope experiments on the bigratings surfaces two-dimensional distortional function profiles are presented.The numerical calculation results satisfactorily agree with the experimental PA angular spectra by choosing proper parameters and shape factors of the bigratings,which illustrates the PA angular spectroscopy combined with theoretical simulation provide a valuable method to Characterize parameters of bigratings.