Abstract: By using the solid polymer electrolysis (SPE) enrichment method and measuring instrument, it is possible to obtain accurate measurements of tritium specific activity for low level tritium sample. However, the differences between current treatment methods for tritium increase uncertainty of the tritium concentrations. In this paper, the methods of SPE electrolysis and alkali electrolysis enrichment (ASE) are used to compare the research results of tritium specific activity for low level environmental water. The reliability of the SPE electrolysis method was improved by using structure optimized apparatus. In order to avoid large uncertainties calculated by the national standard method, the conception of dead volume was introduced into the data processing of the recovery rate for tritium, which improved the stability of the SPE electrolysis method and accuracy of the calculation result.