The invention provides a power transmission line angle-steel tower single and double angle-steel transition joint design method. Joints comprise a crisscross shoe plank on one side of single angle-steel, a crisscross shoe plank on one side of double angle-steel, a transition plate, a single angle-steel main material, the double angle-steel and stiffening plates; the design method comprises the steps of calculating shoe plank height, 2 calculating shoe plank thickness, 3 calculating shoe plank width, 4 calculating transition plate width and 5 calculating transition plate thickness. According to the method, influences of factors such as specifications of the angle-steel main material, the thicknesses of the shoe planks on the upper side and the lower side, and the thickness and width of a horizontal plate are comprehensively considered, the influences of different design parameters on joint stress are researched by building numerical simulation model and conducting entity experiments, design parameters corresponding to the angle-steel of different specifications are summarized according to researching and experimental data, a normative and systematic design method is provided, and a basis is provided for the power transmission line angle-steel tower single and double angle-steel transition joint design. Compared with the current design situation, the method has better normalization and engineering applicability.