A maximal magnetic field measurement method and device. The method comprises: 1. disposing four orthogonally configured tunneling magnetic resistance resistors in an external magnetic field, and acquiring a resistance value of each tunneling magnetic resistance resistor; 2. calculating an included angle between a free layer magnetization direction and a reference layer magnetization direction of each tunneling magnetic resistance resistor according to the resistance values of the four tunneling magnetic resistance resistors; 3. calculating a magnetic field intensity H1 and a direction θ1 of the external magnetic field according to the included angles between the free layer magnetization directions and the reference layer magnetization directions of a first tunneling magnetic resistance resistor (R1) and a third tunneling magnetic resistance resistor (R3), and calculating a magnetic field intensity H2 and a direction θ2 of the external magnetic field according to the included angles between the free layer magnetization directions and the reference layer magnetization directions of a second tunneling magnetic resistance resistor (R2) and a fourth tunneling magnetic resistance resistor (R4); and 4. determining the final magnetic field intensity H according to the magnetic field intensity H1 and the magnetic field intensity H2, and determining the final direction θ of the external magnetic field according to the direction θ1 and the direction θ2.