The reaction activity of tritium separation was obtained using molybdenum nitrides prepared by the temperature-programmed reaction of Moo₃ with NH₃. The molybdenum nitrides had a BET surface area of 87.76 ㎡/g. The molybdenum nitrides were active for tritium separation reaction of tritiated water vapor and hydrogen gas system at temperatures between 323 and 423 K in H₂ flowing at 600 to 800 ㎖/min.