Abstract: The paper discusses the effects of length-to-diameter ratio of cylindrical hohlraum on irradiation nonuniformity of capsule on Shenguang-Ⅲ facility. The parameters of laser spots on hohlraum's inner wall are calculated according to the parameters of Shenguang-Ⅲ facility. The variation of irradiation nonuniformity with the length-to-diameter ratio is analyzed with view factor method for a simplified dual-core irradiation model, and the variations of the best length-to-diameter ratio and irradiation nonuniformity with the albedo of hohlraum's inner wall, power ratio between inner and outer cones and motion of laser spots are also discussed. The calculation results show that the root-mean-square nonuniformity of irradiation is less than 1% at the best length-to-diameter ratio, which agrees