The invention relates to an experimental device for simultaneously establishing different linear gradient temperature fields in a water tank. A base is provided with a transparent water tank and a multi-channel temperature tester; the inner left side wall of the transparent water tank is provided with a semi-conductor refrigerating sheet support provided with a semiconductor refrigerating sheet; the semi-conductor refrigerating sheet support and the semiconductor refrigerating sheet are immersed in water in the transparent water tank; and a front side wall and a rear side wall between the semiconductor refrigerating sheet and the inner right side wall of the transparent water tank are sequentially provided with a first partition plate, a second partition plate and a third partition plate which are separated from the inner bottom of the transparent water tank by a certain distance. With the experimental device of the invention adopted, the technical problem of establishing large-scale linear gradient temperature fields in a transparent water tank can be solved; gradient temperature fields of different linear gradients can be simultaneously obtained in the same transparent water tank; and the transmission differences of light in different linear gradient temperature fields can be easily compared, so that conditions can be provided for quantitatively studying the transmission characteristics of light in gradient index media.