The invention discloses a preparation method and an application of a mesoporous hydroxyl-ferric oxide Cr (VI) adsorbent which can be used for solving the pollution problem of heavy metal Cr (VI) in water. The preparation method of the adsorbent comprises the steps as follows: inorganic iron salt, an amide precipitator and a mesoporous template agent are mixed and dissolved in pure water; the solution is subjected to a hydrothermal reaction after being sealed; a precipitate obtained after the reaction is filtered, washed and dried, and a precursor is obtained; the precursor is calcined and theadsorbent is obtained. The prepared efficient mesoporous hydroxyl-ferric oxide adsorbent has good adsorption capacity for Cr (VI), high saturation adsorption capacity, high adsorption rate and low equilibrium concentration. The raw materials used in the method are cheap, easy to obtain, green and environmentally friendly, the preparation method is simple and adopts mild conditions, and the prepared low-cost adsorbent which has excellent adsorptive performance for highly toxic pollutant Cr (VI) has important scientific significance and good application prospects.