To mitigate the deleterious influence of Distance Measure Equipment (DME) interference on Orthogonal Frequency Division Multiplexing (OFDM) receiver of L-band Digital Aeronautical Communications System1(L-DACS1) operating as an inlay system, a new interference suppression method is proposed based on joint DOA estimation and main beamforming. Firstly, DOA matrix algorithm is used to estimate the DOA of the received signals. Secondly, with the DOA information, Linearly Constrained Minimum Variance(LCMV) beamforming algorithm is utilized to extract the signals in all directions. Finally, frequency-domain power comparison and time-domain power comparison method is proposed to distinguish the received signals and output the direct line-of-sight(LOS) path OFDM signal. Computer simulation results indicate that the proposed method can effectively overcome DME impulse interference and OFDM scattering signal and improve the reliability of the L-DACS1 system.