A method for designing an optical lens with unequal thickness which achieves clear imaging, comprising: S1: establishing a lens model in an optical software, determining the size of the lens model, and preliminarily determining the thickness of the lens model according to the curvatures of an incident surface and an exit surface of the lens model; S2: simulating a beam of incident light, enabling the light to enter through the incident surface and exit through the exit surface of the lens model, and observing whether the incident light and the exit light are parallel; S3: recording the curvatures and thicknesses of the incident surface and the exit surface of the lens model if the incident light and the exit light are parallel, and preliminarily preparing a lens; adjusting the thickness between the incident surface and the exit surface of the lens model until the incident light and the exit light are parallel if the incident light and the exit light are unparallel and designing surfaces with a free variable curvature of unequal thickness, then recording the curvatures and thicknesses of the incident surface and the exit surface, and then preliminarily preparing a lens, wherein the lens prepared in S3 has a lens center and a lens periphery, and the curvature radius of the surface of the lens gradually increases from the center of the lens to the periphery of the lens; S4: arranging a light source and a receiving screen, turning on the light source, placing the receiving screen at different distances from the light source, and recording the positions and sizes of the light projected on the receiving screen, wherein at this point, the position and size of the projected light remain unchanged; subsequently, placing the prepared lens in between the light source and the receiving screen, turning on the light source, placing the receiving screen at different distances from the light source, and recording the positions and sizes of the light projected on the receiving screen; if the position and size of the projected light do not vary, obtaining a finished lens; if the position and size of the projected light vary, returning to S2, repeating S2 and S3 until the position and size of the light projected on the receiving screen remain unchanged after placing the prepared lens in between the light source and the receiving screen, wherein in S4, the light source is an extended light source which emits parallel light, and the incident light is a parallel light. S1: establishing a lens model in an optical software, determining the size of the lens model, and preliminarily determining the thickness of the lens model according to the curvatures of an incident surface and an exit surface of the lens model; S2: simulating a beam of incident light, enabling the light to enter through the incident surface and exit through the exit surface of the lens model, and observing whether the incident light and the exit light are parallel; S3: recording the curvatures and thicknesses of the incident surface and the exit surface of the lens model if the incident light and the exit light are parallel, and preliminarily preparing a lens; adjusting the thickness between the incident surface and the exit surface of the lens model until the incident light and the exit light are parallel if the incident light and the exit light are unparallel and designing surfaces with a free variable curvature of unequal thickness, then recording the curvatures and thicknesses of the incident surface and the exit surface, and then preliminarily preparing a lens, wherein the lens prepared in S3 has a lens center and a lens periphery, and the curvature radius of the surface of the lens gradually increases from the center of the lens to the periphery of the lens; S4: arranging a light source and a receiving screen, turning on the light source, placing the receiving screen at different distances from the light source, and recording the positions and sizes of the light projected on the receiving screen, wherein at this point, the position and size of the projected light remain unchanged; subsequently, placing the prepared lens in between the light source and the receiving screen, turning on the light source, placing the receiving screen at different distances from the light source, and recording the positions and sizes of the light projected on the receiving screen; if the position and size of the projected light do not vary, obtaining a finished lens; if the position and size of the projected light vary, returning to S2, repeating S2 and S3 until the position and size of the light projected on the receiving screen remain unchanged after placing the prepared lens in between the light source and the receiving screen, wherein in S4, the light source is an extended light source which emits parallel light, and the incident light is a parallel light.