In order to confirm appropriate parameters of parallax barrier (PB), a parameter design of PB based on a color Moiré condition in autostereoscopic displays is proposed. Liquid crystal display (LCD) and PB are approximated as the two corresponding binary gratings. Special radial grating is considered as the equivalent model of PB with varying periods and angles. Superposition of the equivalent grating for display device and special radial grating can be analyzed by indicial equations method and Fourier theory. Different predominant low-frequency terms in case of different period of PB can be confirmed. The Moiré-fringe intensity profile in all cases can be obtained by partial sum extraction in Fourier theory. Optimal period and corresponding angle of PB are obtained. Experiment result shows that the autostereoscopic displays have almost invisible Moiré patterns and show good autostereoscopic image.