Depth plane reconstructed by ray tracing algorithm in diffraction limited integral imaging is the refocused image of the object depth. But the image quality is blurring, which is not conducive to three dimensional reconstruction of the object. To solve these problems, a depth plane reconstruction algorithm based on diffraction tracing is proposed. The light field distribution on each optical element surface in the imaging system spread from the point source of the object space, is orderly calculated by the Fresnel diffraction formula, and the intensity pulse response of each sample point on the sensor is obtained finally. Depth plane image is reconstructed by solving the linear equation group related to the intensity pulse response. The simulation results show that the reconstructed image is depth slice of the object, and the image quality is close to the original image, which is beneficial to three dimensional reconstruction of the object.