The invention discloses sodium bentonite and a double sodium modifying method for the sodium bentonite. The method comprises the steps that 1, calcium bentonite and a sodium salt are mixed and modified in a sodium mode to manufacture first-class sodium bentonite; 2, the first-class sodium bentonite and an addition agent are mixed and inoculated to manufacture second-class sodium bentonite, wherein the addition agent comprises microcrystalline cellulose, silica gel modified by a sodium salt, expanded vermiculite, boric acid, a thickening agent and polyacrylamide; the sodium salt and the sodium salt in the silica gel modified by the sodium salt are independently selected from one or more of sodium carbonate, sodium silicate, sodium fluoride, sodium oxalate, sodium acetate, sodium phosphate, sodium polyacrylate, sodium hydroxide, sodium chloride, sodium thiosulfate and sodium cellulose; the thickening agent is selected from magnesium oxide and/or magnesium hydrate. According to the method, the calcium bentonite is fully modified into the sodium bentonite in the sodium mode, moreover, the sodium bentonite has excellent blue absorption power, a high water absorption rate and large colloid indexes, the steps are simple, and the raw materials are easy to obtain.