Abstract: Data-link is an important sub-system of unmanned aerial vehicle (UAV) and a key link to ensure the UAV air-ground communication. However, it is easy to be affected by external electromagnetic interference, leading to communication interruption and even hardware damage. Based on the front-end coupling electromagnetic sensitivity of a certain UAV data link, an equivalent injection test was carried out. The effect law of single frequency and dual frequency electromagnetic interference on data link were studied, and the loss-of-lock threshold of the sensitive frequency points of the data link and the changing trend of the bit error rate and the signal noise ratio were obtained. The results show that:due to the high-power interference signal passing through the automatic gain control (AGC) circuit, the output power of the intermediate frequency (IF) useful signal is reduced in the radio frequency (RF) front end, resulting in a reduction of signal noise ratio (SNR) and an increase in the bit error rate (BER) in data terminal. When the dual-frequency interference is both in-band, the compression effect on the gain of useful signal at the front end is stronger than that of the single-frequency interference. Therefore, when the data-link is out of lock, the threshold of any one of the dual-frequency interference is lower than that of the single-frequency interference, which indicates that a multi-source nonlinear enhancement effect exists in the in-band jamming.