The invention discloses a small magnetic field measurement method, and relates to the technical field of magnetic field measurement. According to the employed technical scheme, the method comprises the steps: 1, collecting the resistance values R1 and R2 of at least two reluctance resistors in a to-be-measured magnetic field, wherein the two reluctance resistors form an inclined angle theta'; 2, substituting the resistance value R1 of one reluctance resistor and the intrinsic parameters of the reluctance resistor into a formula: R=kmcos(theta-theta 0)H+H0, substituting the resistance value R2 of the other reluctance resistor and the intrinsic parameters of the reluctance resistor into a formula: R=kmcos(theta - theta 0 - theta')H+H0, and obtaining binary equation groups; 3, solving the two binary equation groups, and obtaining the magnetic field intensity H and the direction theta of the to-be-measured magnetic field.