The invention discloses a magnetic sensor which comprises a magnetic detection element, an excitation coil and a detection coil, wherein the magnetic detection element is a ferrite; a detection opening is formed in the magnetic detection element; the excitation coil is wound on the magnetic detection element; the detection coil is arranged at the detection opening; the invention also discloses an immunochromatographic chip detection system based on the magnetic sensor; the principle is that superparamagnetic or magnetic nano-particles are used as label probes to prepare a magnetic chromatographic chip. The high-sensitivity immunochromatographic chip detection system based on the magnetic sensor measures a local magnetic field effect generated by particles bound to an immune complex, calculates quantitative results of analytes to be measured, and has characteristics of high sensitivity, high accuracy, easy operation and the like.