The invention discloses a method for reconstructing volumetric imaging in a microscopic light field and its forward process and back-projection acquisition method. Composed of 2D sub-images, the pixel value of each 2D sub-image is zero except for coordinates (i, j); step 2, extract the pixels at coordinates (i, j) on each layer image to rearrange into a single channel image, stack all single-channel images into multi-channel images; step 3, rearrange the 5D point spread function of the light field microscope into a 4D convolution kernel; step 4, use the multi-channel images obtained in step 2 as the convolutional neural network Network input, use the 4D convolution kernel obtained in step 3 as the weight of the convolutional neural network, use the 4D convolution kernel to convolve the multi-channel image, and output the multi-channel image; step 5, rearrange the multi-channel image output in step 4 is the light field image. The invention can greatly increase the convolution calculation speed, thereby improving the image reconstruction speed.