The BWR equation of state modified by Giorgio S. Soave in 1999 was applied to the saturated hydrogen solutions. The parameters needed in the equation of state were modified and optimized through fitting experiment data. p-V-T condition of the saturated hydrogen solutions as well as thermodynamic properties and phase equilibrium of hydrogen fluid can be accurately predicted with this equation. The mean relative error on vapor densities of H2，D2 and T2 was 0.19905%，0.28173%，and 0.001295% respectively. The max relative deviation was -0.99511%

4.6664%

and -0.0040385% respectively. The mean relative error on liquid densities of H2，D2 and T2 was 0.5504%，0.33704%，and 0.04703% respectively.The max relative deviation was 3.2950%，-2.2629%，and 0.12126% respectively. A rigorous thermodynamic model which can be used in simulation of hydrogen isotope-separation by cryogenic distillation was obtained.