The shielding effectiveness of a miniature unmanned aerial vehicle (UAV) has a significant impact on its ability to resist strong external electromagnetic interference. An equivalent method based on a large-scale model is employed to overcome the difficulties of measurement performed inside an extremely small space. In this method, the original miniature UAV is enlarged in proportion with scaling factor n and then a large-scale model is obtained. The shielding effectiveness of the large-scale model can be measured by existing mature instruments and test method. Then, the shielding effectiveness of the original model is obtained according to the relationship between the two models. On this basis, two typical miniature UAVs, i.e., a loitering munition and a quad-rotor UAV, are modeled and simulated. It is validated that the shielding effectiveness of the original model at the frequency f is equal to that of the large-scale model at the frequency $ {f_1} = f/n $. Thus, the proposed equivalent method is correct and effective. Finally, a testing procedure is outlined for the equivalent method. It provides an available way to obtain shielding effectiveness of miniature UAVs.