The invention provides a light guide plate, a manufacturing method thereof and a backlight and belongs to the field of liquid crystal display manufacturing. The light guide plate comprises a light guide plate body, wherein a prism structure is arranged on the first surface of the light guide plate body; the second surface of the light guide plate body is provided with a dimming structure configured to transmit light of a first wavelength and to reflect light of a second wavelength, wherein a target surface of the dimming structure away from the light guide plate body is provided with a latticepoint structure arranged in a manner that the distribution density of the lattice point structure away from a light incidence side of the light guide plate body is smaller than that of the lattice point structure adjacent to the light incidence side of the light guide plate body when the total reflection angle of the light of the first wavelength is larger than the total reflection angle of the light of the second wavelength and the distribution density of the lattice point structure away from a light incidence side of the light guide plate body is greater than that of the lattice point structure adjacent to the light incidence side of the light guide plate body when the total reflection angle of the light of the first wavelength is smaller than the total reflection angle of the light ofthe second wavelength. The invention improves the chromaticity uniformity of the side-entry backlight.