When the ideal three-axis fluxgate sensor measures the magnetic field, its total magnetic field does not change with the attitude change of the sensor. However, due to the limitations of the existing sensor manufacturing and processing technology, the three-axis fluxgate sensor has errors, It may cause hundreds of thousands of nanometers of measurement error, so for high-precision magnetic detection, the analysis and correction of its errors are of great significance. Aiming at the above problems, this topic analyzes the error mechanism of the three-axis fluxgate sensor, establishes a mathematical model for error correction, and uses the ideal three-axis fluxgate sensor modulus value to be independent of the sensor attitude to correct the sensor to correct and compensate the sensor error. The correction algorithm proposed in this paper can complete the error correction of the sensor well, thereby obtaining high-quality magnetic field data, laying a good foundation for the subsequent magnetic target positioning, which has important practical significance.