Abstract: The present invention belongs to the field of pharmaceutical and chemical engineering, and relates to a high-purity losartan potassium and a preparation method therefor. The present invention also relates to a high-purity losartan or a pharmaceutically acceptable salt thereof and a preparation method therefor. The present invention uses organic phosphorus to reduce an azide compound to an amino compound so that the genotoxicity of losartan or a pharmaceutically acceptable salt thereof can be well controlled. The method of the present invention involves fewer steps, uses a small amount of reagent, does not require activated carbon decolorization, and produces a high-purity product, and therefore is suitable for industrial production and is very practical.