Remarkable progress has been made in the technology of weak magnetic field measurement. Breakthroughs in giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR) sensors have driven the miniaturization and integration of sensors applications in biomedicine, geological exploration, and other fields. Based on the theory, the TMR sensor device for measuring weak magnetic by independently made in this work can realize high precision, high sensitivity, directional sensitivity, small size, and low power consumption. The linearity deviation rate of this TMR device is only 0.46% calibrated by using Helmholtz coils, which is linearity and accuracy in measuring magnetic induction intensity. Additionally, the attenuation law of magnetic dipoles in space is experimentally verified. By measuring the magnetic induction intensity of bar magnets in different distances using the TMR device, the inverse cube relationship with distance is confirmed. The TMR device exhibits excellent performance, low cost, and potential for widespread application.