The invention discloses a preparation method of ointment for treating eczema. The preparation method comprises the following steps: respectively weighing cardiospermum halicacabum L, rhododendron dauricum, radix sophorae flavescentis, flos chrysanthemi indici and menthol, soaking the cardiospermum halicacabum L, rhododendron dauricum, radix sophorae flavescentis, flos chrysanthemi indici and menthol with deionized water, decocting with slow fire after boiling with strong fire, filtering medicine residues to obtain an extracted medicine liquid, heating the extracted medicine liquid and concentrating to be viscous to obtain the concentrated medicine liquid; sequentially adding an antioxidant, an emulsifier, an emollient, a humectant, a co-emulsifier, a thickener, a preservative and a preservative synergist into the concentrated medicine liquid, adding the deionized water, stirring the materials, and uniformly mixing the materials to obtain the ointment for treating eczema. The ointmentdisclosed by the invention contains various moisturizing components, and can maintain moisture in skin tissues, improve the water shortage state of the skin and moisten the skin tissues; the skin injury is effectively repaired, the skin resistance and skin elasticity are enhanced, and the skin is protected.