In measurement of magnetic axis of solenoid, there are some key difficulties to overcome, such as precision measurement of tuat-wire vibration and position, reducing measurement signal distortion, and separative data processing for offset and tilt signal in magnetic axis of solenoid. One kind of signal detect and measurement principle of extracting the useful faintness signal via subtracting the high offset level signal from the total measurement signal is adopted to meet the above need. The method of constant current driving the detector is also adopted to obtain more stable and anti-jamming signal. The measurement system has been developed for directly obtaining the pure vibration signal of the tuat-wire. The problems of obtaining completely exact measurement signal by simply using an AC coupling amplifier or band-pass filter are resolved and the faint signal can be obtained without aberration. The influence produced by tilt and ups-and-downs in low frequency component of base line signal is eliminated ulteriorly. The separative data processing for offset and tilt signal is also achieved to some extent. The measurement sensitivity has been improved maximumly by about an order of magnitude.