This invention describes a magnetoresistive inertial sensor chip, comprising a substrate, a vibrating diaphragm, a magnetic field sensing magnetoresistor and at least one permanent magnet thin film. The vibrating diaphragm is located on one side surface of the substrate. The magnetic field sensing magnetoresistor and the permanent magnet thin film are set on the surface of the vibrating diaphragm displaced from the base of the substrate. A contact electrode is also arranged on the surface of the vibrating diaphragm away from the base of the substrate. The magnetic field sensing magnetoresistor is connected to the contact electrode through a lead. The substrate comprises a cavity formed through etching and either one or both of the magnetic field sensing magnetoresistors and the permanent magnet thin film are arranged in a vertical projection area of the cavity in the vibrating diaphragm portion. A magnetic field generated by the permanent magnet thin film changes in the sensing direction of the magnetic field sensing magnetoresistor of magnetoresistive inertial sensor chip, which changes the resistance valve of the magnetic field sensing magnetoresistor, thereby producing a change in an output electrical signal. This magnetoresistive inertial sensor chip uses the high-sensitivity and high-frequency response characteristics of a magnetoresistor to improve the output signal strength and frequency response, thereby facilitating the detection of small and high frequency pressure, vibration, or acceleration changes.