In order to detect the profile of holographic photoresist grating mask made on top of chrome stack, rigorous coupled wave theory (RCWT) was applied to analyze the relationship between zero order reflected spectrum and the profile of grating mask. Zero order reflected spectra range from 400 nm to 700 nm at the incident angle of 60° were measured in experiment. The standard deviation of differences between experimental curve and theoretic curve of different profiles is calculated for matching,and the duty cycle and groove depth were obtained by the best fitted theoretic spectra corresponding to minimum standard deviation. Results achieved in this way which is a quick in matching and high in error tolerance, agree very well with scanning electron microscope (SEM) pictures. The method is qualified for measurement of groove depth and duty cycle simultaneously for the rectangle-shaped or similar profile of holographic grating mask.