This article establishes a physical model of the interaction between a surface electron beam and the plasma with a transverse magnetic field. The dispersion relation of the beam-plasma interaction is derived by using the field matching method. The effects of magnetic field, electron beam electron density, and plasma density on the radiation frequency and z-direction wave vector are studied. The results indicate that the stronger the transverse magnetic field is, the higher is the cutoff frequency of plasma radiation. The higher the plasma density or electron beam electron density is, the higher are the corresponding radiation frequency and radiation wave number.