In order to study the magnetic field distribution and temperature rise of marine Variable Frequency Drive (VFD) cables, the two-dimensional section model of the VFD cables is established and the finite element software is used to simulate the magnetic field and heat loss under normal operating conditions and open-phase conditions. The simulation results of magnetic field show that under different working conditions, the low-frequency magnetic field at a distance of 500 mm from the VFD cables has less magnetized effect on the hull, and the magnetic flux density will not exceed the human safety limit specified by the standard. The simulation results of natural convective heat loss show that when the current of the non-fault phase rises, the temperature of the VFD cables will exceed the temperature limit of 85 ℃ when a open-phase fault occurs in the system, while the motor and the VFD cables require reasonable control and protection strategies, and the ventilation should be strengthened.