The invention provides a winding measuring instrument comprising a constant current source circuit and a fluxgate sensor. The constant current source circuit outputs a constant current, and the output of the constant current source circuit is connected to a first turn coil and all coils of a winding respectively. The fluxgate sensor is used for detecting a magnetic field of the coils of the winding, and the output of the fluxgate sensor passes sequentially through a sensing signal conditioning circuit and an A/D conversion circuit and is then connected to a controller. The controller calculates the turns of the winding according to a signal outputted by the A/D conversion circuit. According to the invention, since the output of the constant current source circuit is connected to the first turn coil and all the coils of the winding respectively, the magnetic field after power-on is measured by the fluxgate sensor and the controller calculates the turns of all the coils of the winding and determines a current direction of the coils of the winding according to the detected size and polarity of the magnetic field, the degaussing cycle is effectively shortened and the degaussing efficiency is improved.