The invention provides a flotation column system and method for storing high-concentration pulp. The system mainly comprises a feeding pipeline, an upper flotation column, a lower flotation column, a returning pipeline, a scavenging pulp circulating pipeline and a tailings box. The method comprises the following steps: connecting the upper flotation column and the lower flotation column in series by a staggering manner; pumping in the pulp through a feeding pump; performing flow mineralization through a generation pipe of an upper bubble generator; enabling the material that has relatively high flotation to be preferably floated in the upper flotation column and discharged through a concentrate bin; feeding the materials that are not sorted timely into the lower flotation column for further storing through the returning pipeline under the control of a peristaltic pump. According to the flotation column system and method for storing the high-concentration pulp, the material with high flotation is pre-floated through the upper flotation column in order to lower down the concentration of the pulp entering the lower flotation column, and thus the effects of pre-sorting by the upper flotation column and highly storing by the lower flotation column is realized, sectional floating and sorting are realized, and as a result, the technical problem that the high-concentration pulp flotation clean coal quality and clean coal recovery rate cannot be ensured at the same time can be solved, and thus the phenomena of pollution of the clean coal and running of tailings are greatly reduced.