The invention discloses a steel wire rope magnetic memory on-line detection device, and belongs to the technical field of non-destructive detection. The steel wire rope magnetic memory on-line detection device includes two groups of three-dimensional magnetoresistive sensors, adders, multipliers and subtracters, the two groups of three-dimensional magnetoresistive sensors are mounted on a steel wire rope and have the same mounting direction, and each group of three-dimensional magnetoresistive sensors comprises 8-12 three-dimensional magnetoresistive sensors uniformly distributed at a same circumference. An equilibrium and differential detection method is adopted to mainly aim to overcome steel wire rope shaking and outside interference, secondary output of signal characters is carried out, and the accuracy for judging metal member defects is improved; secondly, with adopting of a component signal single output method, whether a point is a steel wire rope defect is judged according to characteristic signals singly outputted by a normal component and a tangential component; and then, the two groups of annular uniformly-arranged three-dimensional magnetoresistive sensors HMC1053 are adopted to achieve all-dimensional inspection of the normal component and the tangential component of the steel wire rope, so as to eliminate the measured blind area problem.