Abstract: This paper introduces the system composition of grid GNSS weak interference source location. Aiming at the problem that the existing methods have poor adaptability to low signal-to-noise ratio (SNR), this paper proposes a grid GNSS weak interference source localization method based on Mean Function of Difference Square based on Separation of signal and noise (MFDSS). The method uses MFDSS method to realize time difference estimation, and Chan hyperbolic positioning algorithm is used to calculate the location of interference source. This paper compares and simulates the positioning effect of this method and the commonly used grid positioning method. The results show that the method has superior performance in the GNSS weak interference source localization scene.