Abstract: There are many kinds of nondestructive testing methods, and the electromagnetic detection method is adopted in LF type and LMA type of in-service steel wire rope. Nondestructive testing instrument for steel wire rope is based on the principle of permanent magnetic excitation, acquisition defect signal by Hall element sensor. In the actual detection, good effect is achieved on LMA type defect. Owing to the limit of detection technology and the influence of steel wire rope structure, LF type defect can not be quantitatively analyzed. Semi quantitative method for LF type defect is not accurate. If quantitative analysis of LF type can be solved and the relationship between defects and strength can be known,then the service life of in-service steel wire rope is able to be accurately predicted.