In order to study the magnetic signal in ship piping generated under the rolling condition, a large piping model is established, and the ANSYS finite element software is used to respectively simulate the changes of loop current before and after setting the electrical insulating materials. The obtained current values are taken as the input, and the size of harmful magnetic signal is obtained quantitatively through the static magnetic field simulation. The results show that the induced current in ship piping is greatly reduced after setting the high-resistance materials, and the harmful magnetic signal generated in large loop is correspondingly reduced.