Disclosed are an image processing method and device, and a three-dimensional imaging system. The method comprises the following steps of: acquiring a two-dimensional image to be processed; aligning the two-dimensional image to be processed to a grid template; performing mapping processing on the two-dimensional image to be processed by using a grid mapping table to acquire a first image, wherein the grid mapping table is used for representing the mapping relationship of grid images; mirroring the first image to acquire a second image; and synthesizing the first image and the second image to acquire the superimposed image of the first image and the second image. According to the method, the grid template and the grid mapping table are used for performing mapping processing on the two-dimensional image to be processed so as to simulate a left-eye image and a right-eye image acquired by human eyes; and a same two-dimensional image to be processed need to be mapped only once to acquire the left-eye image and the right-eye image, the steps of image processing being reduced, thus the time of image processing being shortened, and providing favorable conditions for the follow-up real-time conversion of the superimposed two-dimensional image into a three-dimensional image.