Abstract: When radial shear interferometer is used in high-power laser wavefront detection, due to the influence of the nonlinearity of CCD, there exist not only the first order frequency with wave-front information but also the second and the third order frequency. They may lead to overlapping spectrum, which makes it difficult to extract useful information and reduces the detection accuracy of wavefront. A theoretical analysis on mechanisms of high-order spectral component and spectrum aliasing caused by the nonlinearity of CCD is established, and the condition to avoid spectrum aliasing is pointed out. Finally, a method by increasing the spatial carrier frequency to reduce or eliminate the spectrum aliasing is proposed. Computer simulation and experimental results have verified the feasibility of