Recent theoretical work has proved that conventional Kirchhoff’s law does not hold for every material and only holds for reciprocal materials. Zhang et al. have derived the generalized Kirchhoff’s law, which holds for both reciprocal and nonreciprocal materials [JQSRT 245, 106904 (2020)]. However, the verification of the generalized Kirchhoff’s law for nonreciprocal materials in experiments has not been reported until now. The main reason is that the proposed structures could only realize strong nonreciprocal radiation at wavelength larger than 10 μm, however, the emissivity is hard to be accurately measured in this band with existing measurement technologies. Here, we proposed a planer structure to realize strong nonreciprocal radiation near wavelength of 10 μm at room temperature with an external magnetic field 3 T. The strong nonreciprocal radiation is attributed to the coupling between the guided modes inside the magneto-optical materials and the evanescent waves provided by the prism via attenuated total reflection. With existing absorptivity and emissivity measurement methods, it is promising and practicable to verify the Kirchhoff’s law for nonreciprocal materials in the proposed structure.