Objectives  In order to achieve the fast and high quality demagnetization of ships, a new demagnetization technique adopting a ring-shaped working coil is proposed.

  Methods  First, the electromagnetic design of the demagnetization facility with a ring-shaped working coil is studied comprehensively, including the main framework, theoretical analysis, simulation and calculation of electromagnetic data. Next, in the north-south direction and east-west direction, a model of the demagnetization facility with a ring-shaped working coil is constructed and demagnetization tests carried out on models of two types of surface ship and two types of underwater ship. Finally, the feasibility of the demagnetization facility with a ring-shaped working coil is analyzed.

  Results  The theoretical analysis and ship model test results show that the demagnetization facility with a ring-shaped working coil has advantages in the east-west direction because of the easily adjusted demagnetization currents, good demagnetization results, very fast demagnetization speed and low construction cost advantage.

  Conclusions  The results of this paper show that this proposal is especially suitable for the demagnetization of underwater ships.