This paper proposes a fault line detection method based on cross correlation coefficient for distribution network which has distributed generation (DG). Firstly, Genetic Algorithm (GA) is used to optimize the potential function parameters of bistable system (BS), and bistable system is utilized to extract zero-sequence current in noise background. Then, as for fault line detection criterion, the cross correlation coefficient is calculated between different lines, and the line which has smallest comprehensive correlation coefficient is judged as fault line. At last, simulation experiments prove that the method can detect fault line exactly in different fault environment, including different grounding resistance, fault distance and so on.