Magnetic flux leakage (MFL) testing is a common method in nondestructive testing of wire rope. Based on the basic principle of MFL detection and threedimensional magnetic dipole model, this paper realizes  the visualized online detection of wire rope by using By~Bz diagram. The characteristics of MFL defects of different lengths, widths and depths are obtained by using finite element simulation method, the quantitative relationship between the MFL circle in By~Bz diagram and the degree of defects is established. The difference of magnetic leakage caused by internal and external defects of wire rope is discussed, and experimental verification is carried out in order to provide a new theoretical basis for quantitative identification of wire rope damage and judgment of internal and external defects.