The invention discloses a sodium nitrate preparation method which specifically comprises the following steps: (1) by taking sodium bicarbonate and nitric acid as raw materials, washing the raw material sodium bicarbonate with a cleaning liquid, and performing solid-liquid separation so as to obtain solid phase sodium bicarbonate and a liquid phase waste washing liquid; (2) mixing the solid phase sodium bicarbonate and the raw material nitric acid, and performing solid-liquid neutralization reaction so as to obtain a reaction mixture after the reaction is completed; (3) treating the reaction mixture obtained in the step (2) by using a concentration method, thereby obtaining a final product sodium nitrate. By adoption of the sodium nitrate preparation method disclosed by the invention, sodium nitrate of a superior grade can be prepared, or even sodium nitrate of a food additive grade can be produced, and moreover the sodium nitrate preparation method disclosed by the invention is environment-friendly and energy-saving, and remarkable in economic benefit.