Aiming at the low accuracy of interferometer direction finding (DF) with low signal-to-noise ratio (SNR), a new adaptive direction finding method is proposed based on SNR estimation and phase-difference vector averaging. This method can enhance the accuracy and stability of the phase-difference measurement through multiple measuring and averaging the phase-difference complex vectors, which can improve the performance of the direction finding. The proposed adaptive criterion can estimate SNR of the arrival signal and quickly determine the required sample size, therefore adjust the sample size adaptively at different SNRs and obtain the stable accuracy of DF. The effect of SNR threshold on the performance of the proposed method is analyzed. The method holds a low computational complexity and has little influence on real-time of DF.Theoretical analysis and simulation results reveal that the method can achieve high accuracy even under very low SNR conditions, and improve the DF performance obviously.