The　unusual　electronic　properties　of　3-D　topological　Dirac　semimetals　have　led　to　intensive　research　efforts　focusing　on　their　potential　applications　in　high-performance　electronic,　photonic,　and　optoelectronic　devices.　In　this　work,　we　propose　a　conceptual　design　of　thermionic　energy　converters　(TECs)　based　on　a　Cd3As2　anode　with　significantly　improved　performance.　Using　the　electronic　properties　of　Cd3As2-an　air-stable　topological　Dirac　semimetal-from　first-principle　density　functional　theory　(DFT)　calculation,　such　a　device　can　achieve　a　maximum　output　power　density　and　conversion　efficiency　of　10.96　W/cm(2)　and　57.29%　at　1800　K,　respectively.　The　advantages　of　topological　Dirac　anode　over　conventional　metal-　and　graphene-based　TECs　are　revealed.　This　work　opens　an　exciting　route　toward　high-performance　energy　converters　via　the　union　of　topological　material　and　thermionic　devices.