Abstract: In a distributed antenna arraying system, an effective large aperture with low cost can be realized by utilizing the existing antenna resources. For the receiving signal-to-noise ratios(SNRs)of antennas with different apertures in distributed antenna arraying system vary in a large range,a question is raised that is the combined performance improved with arbitrary antennas added into the distributed antenna arraying system? An optimal design criterion is proposed to solve this issue. Based on the estimation algorithm's performance and the Cramer-Rao bounds (CRBs)of carrier frequency, delay and carrier phase, the criterion proves. that the combined BER performance is degraded when antennas with receiving signal's SNR lower than the outlier effect threshold of carrier frequency estimation are added to the distributed antenna arraying system. Theoretical analysis and simulation results verify the above conclusion.