Abstract: According to the environmental characteristics of nuclear power ships, a passive sampler with a volume ratio of ethylene glycol to tritium-free water of 1:1 is used to monitor the concentration of tritiated water in a closed nuclear power plant. After continuous monitoring for 1 month in different work places, it is found that the maximum relative deviation of the sampler was less than 10%; Sampler has been compared with the passive sampler with silica gel as the adsorption medium for 1 day comparison experiment, and the measurement error is less than 6%. Results show that the sampler can accurately measure the low concentration of HTO, which meets the monitoring requirements of HTO in closed nuclear power plants.