Abstract: With the increase of power aperture product, the requirement of airborne early warning radar on system phase noise level is becoming higher and higher. Firstly, the main factors that affect the phase noise in digital array radar are analyzed, and a digital array radar model with distributed phase-locked loop for the short board of system phase noise is constructed in this paper. This model generates uncorrelated noise in each channel through an independent phase-locked loop, which improves the overall phase noise level of the system in beamforming. Then, the impact of the phase-scanning angle on the phase noise in beamforming is discussed in this paper, and the phase noise changes of the radiation signal from the main lobe and side lobe are considered, which provide ideas for the design of the airborne early warning radar system. Finally, simulation experiments verify that the distributed phase-locked loop architecture improves the phase noise of the system, and beamforming worsens the phase noise of the side lobe radiation signal.