The optical system of the head-mounted display is prone to image distortion generally because its focal length is short and its field of view is wide. An image distortion measurement method of head-mounted display is presented. A Fourier transform image of unit matrix is chose as standard test pattern, and the relationship between optical transfer function of head-mounted display and spherical distortion of image is analyzed with Fourier transform. Based on this method, the similar relationship curve are obtained. Image spherical distortion of five kinds of head-mounted display are measureds, and the negative-pinched pincushion distortion is obtained which ranged from -22% to -65%. The results show that spherical distortion CVR of the head-mounted display has linear relation with distortion quality of grid image measurement. However, the measuring method for spherical image distortion is simple, and the measuring results can reflect the distortion of the whole image. The results are of great reference value for measuring image quality of head-mounted display.