Abstract: Tritium in urine of tens of the workers in the course of the decommissioning is determinated by distillation and liquid scintillation counter, whose cncentration are 10 2～10 5 Bq/L and whose maximum concentration is 2.7×10 5 Bq/L, which is dose equivalent 0.19 mSv by counted. The half time of tritium excretion of 23 workers are 5.5～14.8 d and the average value is 9.1 d in short time. The half time of tritium excretion of 5 workers are 7.6～9.4 d and the average value is 8.5 d in middle time. The half time of 28 workers in the work not only comes near to theoretical value 10 d, but also fully tallys with internal and external observated value.