Abstract: In order to investigate sufficiently the lockout law of the navigation receiver's tracking loop under multi-source electromagnetic interference, a model of the lockout effect of the tracking loop under dual-source electromagnetic interference was studied. Analyzing the mathematical model of the equivalent carrier-to-noise ratio of the correlator output under electromagnetic interference, a model of the tracking loop lockout effect under dual-source electromagnetic interference was established. Then an experiment platform was set up with a single-source and dual-source electromagnetic interference to carry out an injection experiment for the Beidou navigation receiver. During the experiment, four different combinations of interference signals were selected, and under the experiment of each combination, different signal power combinations were obtained. Finally, the experiment data were used to verify the effect model, showing the model errors all within 1.5 dB. This model reveals the internal relationship between dual-source and signal-source interference in the navigation receiver tracking loop, providing a guide for further research on the law of navigation receiver effect.