The invention discloses Zn-Cu doped magnesium oxide nano-powder and a preparation method thereof. The preparation method specifically comprises the following steps: by taking magnesium acetate, zinc acetate and copper acetate as raw materials, mixing, evaporating, drying, and thermally treating for twice, thus obtaining the Zn-Cu doped magnesium oxide nano-powder; the Zn-Cu doped magnesium oxide nano-powder contains magnesium oxide, zinc oxide and copper oxide, and has a general formula of Mg1-xZnx-yCuyO, wherein x is greater than or equal to 0.05 and less than or equal to 0.1, and y is greater than 0 and less than x; the Zn-Cu doped magnesium oxide nano-powder has the crystalline grain sizes of 5 to 30nm and the specific surface areas of 100 to 300m<2>/g. The obtained Zn-Cu doped magnesium oxide nano-powder has different grain sizes and different specific surface areas, and can serve as a catalytic additive for improving solid propellant performance.