Abstract: Integrated pole piece (IPP) type interaction system has great application potential in high frequency traveling wave tubes and it is a very important problem to reduce transverse magnetic field in its design and application process. This paper Introduced structure unit, working principle and comparative advantage of IPP. Based on a specific IPP geometry, the paper firstly made a qualitative analysis on key parameters effecting magnetic field distribution, and then a detailed study of the relationship between each parameter changes and magnetic field distribution was developed using CST static magnetic studio. The results not only can deepen the understanding magnetic field distribution of rectangular magnet, but also has laid the foundation for the application of IPP interaction system in high frequency traveling wave tubes.