The invention discloses a method for preparing pigment-grade chromium oxide green. The method comprises the steps of taking reducing gas as a reducing agent, allowing chromic salt to react with the reducing gas for 1-2 hours at a temperature between 300 and 550 DEG C, cooling, using water to wash and hydrolyzing a reaction mixture, mixing the reaction mixture with additives at a temperature between 900 and 1,100 DEG C, activating and sintering the reaction mixture and the additives for 1-3 hours, washing, drying and grading the sintered material to obtain the pigment-grade chromium oxide green, wherein the chromic salt is chromate or bichromate; the reducing gas is hydrogen, natural gas, ammonia gas, coal gas or a mixture thereof; and the additives are silicon compounds, titanium compounds, boron compounds, phosphorus compounds, aluminum compounds, barium compounds, zinc compounds and other compounds, such as SiO2, TiO2, K2TiO3, HBO3, H3PO4, P2O3, Al2O3, Al(OH)3, BaO, Ba(OH)2, ZnO, Zn(NO)3, Sb2O3, Sb2O3 and other substances.