Tritium based betavoltaic nuclear battery exhibits significant potential for use in various fields due to their high energy density, long lifespan, and stable output performance. This study simulated the self-absorption effects and the surface emission power of seven typical tritium storage materials using the Monte Carlo method. Three tritium storage films (MgT ₂ , Mg ₂ YT ₇ , and TiT ₂ ) with superior tritium storage performance were determined, and their thicknesses were optimized. Subsequently, the energy deposition distribution of the radioactive sources in the semiconductor converter was simulated, and the model of SiC based PIN betavoltaic nuclear batteries with different tritium storage films was constructed to predict the electrical output performances of batteries. The influence of film thickness and tritium storage capacity on the output performance of batteries was also analyzed. The simulation results showed that the optimal thicknesses of MgT ₂ , Mg ₂ YT ₇ , and TiT ₂ films are 1.75 μ m, 1.0 μ m, and 0.75 μ m, respectively, and the corresponding SiC based betavoltaic nuclear batteries can achieve the maximum output power densities of 0.310 μ W cm ⁻² , 0.233 μ W cm ⁻² , and 0.196 μ W cm ⁻² , respectively. The performance of MgT ₂ and Mg ₂ YT ₇ sources betavoltaic nuclear batteries is superior to that of TiT ₂ source.