Abstract: Provided in the present disclosure are a nemonoxacin malate active pharmaceutical ingredient with low combination impurities, and a preparation method thereof, specifically, provided in the present disclosure is a method for preparing the nemonoxacin malate active pharmaceutical ingredient, the method includes the following steps: 1) providing a C1-C3 alcohol/water mixed solvent in which nemonoxacin free base (Formula II) and D,L-malic acid are dissolved; and 2) performing cooling crystallization on a mixed solution obtained in the step 1), and then performing solid-liquid separation, washing and drying on a precipitated solid, so as to obtain the nemonoxacin malate active pharmaceutical ingredient.