Submarine cable fault accurate positioning method based on magnetic vector data and positioning instrument

The invention relates to a submarine cable fault accurate positioning method based on magnetic vector data and a positioning instrument. The method is characterized by comprising the following steps of 1), connecting a high-power alternating current source with a faulty submarine cable, and outputting a sinusoidal current signal I0sin (omega t) with stable frequency and stable amplitude; 2) connecting a water surface towed body for measuring data with a shipborne upper computer on a measuring ship by using a watertight cable, wherein the measuring ship drags the water surface towed body to move from the power supply end of the faulty submarine cable along the laying direction of the faulty submarine cable; 3) based on the frequency omega detected by the water surface towed body as an alternating magnetic field signal, calculating to obtain a longitude coordinate lon2 (t1) and a latitude coordinate lat2 (t1) of the faulty submarine cable; and 4) according to the obtained longitude and latitude coordinates lon2