The mid-infrared light emitting diodes based on the interband cascade structure and resonant cavity structure are simulated and designed. Based on the traditional interband cascade LED, a distributed Bragg reflector (DBR) structure is introduced outside the device to form a resonant interband cascade LED. The parameters of the resonant cavity are simulated and optimized, including the number of DBR cycles, the length of the resonator, the position of the active region in the resonator, and the optimized device structure is obtained. The simulation results show that the device using ZnS/Ge DBR with one period as the upper mirror of the resonator has the highest output power. When the active region is located at the peak of the electric field intensity in the resonant cavity, the device will have the highest output power. The output power of the three-stage resonant cavity interband cascade LED device is equivalent to that of the 55-stage device without a resonant cavity. Meanwhile, the output light has a better direction, and the full width at half peak of the far field distribution can be reduced from 92 degrees to 52 degrees. Combined with the test results of the fabricated 5-stage interband cascade LED device, the simulation results after adding a resonant cavity structure indicate that the radiance of the peak wavelength is increased by 11.7 times, the integrated radiance is increased by 5.43 times, and the full-width at half-maximum is narrowed by 6.45 times.