The resistance of transceiver combination（as a core component of Unmanned Aerial Vdehicle（UAV） data link system） to electromagnetic interference directly affects airborne communications security. In order to verify the reliability of UAV data link system under radiation condition of the nuclear electromagnetic pulse（HEMP）

we built a test platform based on the fast along the electromagnetic pulse simulation system. Typical "unlock" effect was regarded as discrimination of interfered accordance to conduct a research of radiation effects and to analyze the "unlock" effect mechanism of UAV data link. Experimental results show that HEMP does interfere with UAV data link test system when it reaches 72 k V/m

which results in the phenomena of completely unclock and black screen on flight control simulator. Besides

changing the attitude of transceiver combination does not affect the interference threshold of basic data link system. Through electromagnetic simulation analysis

instantaneous power interruption of transceiver combination due to terminated cable of flight control simulator coupling strong external field signal will directly interfere the data link. Exclusive of flight control simulator of the data link test system

when the radiation field strength is less than 90 k V/m

the UAV downlink telemetry link does not appear to lose lock.