Abstract: To test and evaluate the adaptability of the spectrum-dependent equipment to complex electromagnetic environment, introducing a LF blocking interference factor and the relative value of LF interference level, a second-order intermodulation LF blocking effect model was established to investigate the mechanism of second-order intermodulation LF blocking effect. Combining theoretical derivation and experimental measurement, a method was provided to determine the model parameter, the modeling and evaluating processes were established for the second-order intermodulation LF blocking effect. Finally, taking a satellite navigation receiver as the test equipment, an experimental verification was carried out. The results show that, using the second-order intermodulation LF blocking effect model parameters of the equipment under test at a specific working frequency, according to the tested data of the critical interference field strength of the single frequency electromagnetic radiation blocking and the distribution parameters of environmental electromagnetic field spectrum, the second-order intermodulation LF blocking effect of the spectrum-dependent equipment can be objectively evaluated, error is within 2 dB.