Abstract: Seven tritiated water samples of 0.5 Ci/ml to 35 Ci/ml are employed. The~3H NMR signal intensity increases in propotion to the radioactivity determined byliquid scintillation counting. The double ~3H NMR signal from tritiated water(J_(TH)=0.59 Hz, 25 Ci/ml at 30±1℃) is observed. The rate constant for the ex-change between triton and proton is 2.62 S~-. The ~3H NMR spectra as a functionor time provide the information about self--radiolysis of tritiated water.