A new type of multilayer thermionic coolers with varying barrier heights is proposed in this article. Based upon the assumption of ballistic electrons in the filters and thermalized electrons in the bases, we analyzed the energy balance at each stage. As the heat flux increases at later stages, the barrier height should also increase. The optimum structure is obtained by a trial-and-error method. Calculation results show that the coefficient of performance does not change significantly with the number of stages of the thermionic cooler. The heterojunction structure with varying barrier heights have a slightly higher COP than the one with a fixed barrier height.