The wire rope nondestructive testing principle based on localized fault(LF) and loss of metallic cross-sectional area(LMA) is introduced and a measuring method based on magnetic flux leakage is proposed in this paper.By using permanent magnetices to magnetize permanently wire rope and using Hall effect sensors to test magnetic flux,the relationship of peak-peak value in magnetic flux leakage and wirerpoe sectional area is analyzed and studied,then proportional relationship and aided quantification of which is given.A kind of intelligent wire rope nondestructive testing instrument is designed which is based on this algorithm of testing radial magnetic flux leakage of wire rope by Hall sensor.And the LF testing is introduced in detail.The instrument is controlled by AT89C51 microchip computer,and easily operated.