The magnetic sensors based on giant magnetoimpedance (GMI) and asymmetrical giant magnetoimpedance (AGMI) effects of amorphous alloy materials are one of the research hot spots in the magnetic sensor technology field over the past two decades. Amorphous alloy material has been believed to be the material suitable for developing the micro magnetic sensors with high resolution, low power consumption and fast response speed. However, up to now most of the GMI sensors with high resolution developed at abroad are at the preindustrial prototype stage, and their basic performance specifications are inferior to the commercial AMR and GMR magnetic sensors. This paper briefly describes the influence of the GMI effect in amorphous alloy material and annealing processing on GMI effect. Then, the paper emphatically introduces various types of amorphous wires and ribbons based GMI magnetic sensors developed abroad, analog signal detection circuits and their reference performance specifications. Finally, the key techniques for developing high sensitivity GMI magnetic sensors are investigated with an outlook of future research in this field.