The invention discloses a three-dimensional transient magnetic field measuring system which comprises a three-dimensional magnetic field measuring probe, a three-dimensional signal synthesis unit, anoptical fiber transmission unit and a signal processing unit that are successively connected; the three-dimensional magnetic field measuring probe comprises an insulating counterweight base, an organic glass supporting column and three magnetic field probes; the organic glass supporting column is vertically fixed on the insulating counterweight base, and the three magnetic field probes are respectively a three-dimensional Y-axis vertical direction magnetic field B-dot probe, a three-dimensional Z-axis vertical direction magnetic field B-dot probe and a three-dimensional X-axis vertical direction magnetic field B-dot probe. The three magnetic field probes are fixed on the organic glass supporting column. According to the invention, the transient magnetic field measurement is carried out byadopting three-dimensional hardware synthesis under severe electromagnetic working conditions, and the system can be applied to the fields of electric power, military, aviation, aerospace, and railways needing three-dimensional transient magnetic field measurement.