The invention relates to a downhole reversal gravel throwing tool. The gravel throwing tool comprises an external gravel throwing component and an inserting pipe inserted in the external gravel throwing component; the main body structure of the external gravel throwing component is an external pipe, a coupling is arranged at the top of the external pipe, and four uniformly-distributed gravel throwing holes A are formed in the same horizontal plane in the middle; stop blocks are arranged on the position, above the gravel throwing holes A, of the inner surface of the external pipe, a groove is formed in the position under each gravel throwing hole A, guiding rails are arranged under the grooves, and dowels are arranged under the guiding rails; sliding sleeves are arranged in the guiding rails; and pawl springs are arranged on the sliding sleeves, and a gravel throwing hole B is formed in the middle of each of the four pawl springs. According to the downhole reversal gravel throwing tool, the improved sliding sleeve are adopted for opening and closing, and thus achieving of opening and closing of the gravel throwing holes can be facilitated; and the effect that gravel materials in a gravel throwing pipe do not slip into the well bottom after gravel throwing is finished and are reserved in the gravel throwing pipe and taken out from a mouth of the a well can be ensured.