The invention discloses a variable magnetic field high-temperature melt oscillation viscometer and a rapid measurement method thereof. The viscometer comprises a central plate, a measurement container is supported by the upper portion of the central plate, and the lower portion of the central plate is connected with a heating device; the measurement container is internally provided with an oscillation system, the oscillation system comprises a rotary power device, the bottom of the rotary power device is connected with a measurement rod through a suspension fiber, and the bottom of the measurement rod is connected with a sample containing device in the heating device; the suspension fiber is provided with an optical measurement system for measuring the logarithmic decrement; the heating system is sleeved with a magnetic field system with the magnetic field direction and intensity adjustable so that the heating device can be located in a variable magnetic field. The magnitude and direction of a magnetic field where a sample is located are adjusted by changing the current and the number of windings of a magnetic field coil, the optical measurement system obtains the logarithmic decrement of the oscillation system through a laser signal reflected by a reflector, and viscosity data of the sample are obtained according to the relation between the viscosity and the logarithmic decrement.