To resolve mutual restriction of viewing angle and luminance, a high luminance integral imaging display based on a gradient line light source was proposed. The light paths of the elemental images in the element image array were optimized by adjusting the widthes of the line light sources in the gradient line light source. The imaging model of the integral imaging display based on the gradient line light source was established. The calculation formulas of the viewing angle and luminance were obtained by using geometrical optics. An experimental apparatus of the integral imaging display based on the gradient line light source was built. The experimental results prove that the luminance of the 3D image is 4.5 times of the conventional one without loss of the viewing angle.