The structure of distribution network is becoming more and more complex and the limitation of traditional fault location method is dominant. A fault location method is proposed which is suitable for complex distribution network. This method makes use of characteristics of voltage sag and information collected by power quality monitor， then fault can be located by correlation analysis. Simulations on IEEE 37-bus system and IEEE 13-bus system show that this method can effectively prevent misjudgement. Test results also show that the proposed method has better robustness and error tolerance capability， as load model， transition resistance and loading of transformer are concerned.