Abstract: In order to study the electron-emitting characteristics and decay effect of titanium tritide source films in betavoltaic batteries, the transport and emission behavior of electrons from tritium in the source films were studied. The apparent activity density, electron emission energy spectrum and apparent electron power of the source film were obtained, and the decay of the above performance indicators over time was evaluated. So as to provide a theoretical basis for the development of β-radiation volt effect isotope batteries with tritium as the radiation source. By capturing, fitting and discretization, the discrete energy spectrum of electrons from tritium decay was obtained for energy sampling of input electrons. On this basis, the Monte Carlo method was used to simulate the apparent activity density and electron emission energy spectrum of the source films, further calculated the apparent electron power, and analyzed the self-absorption effect and decay effect of the source films performance. At the same time, the high-purity titanium films were prepared by magnetron sputtering method. And after the tritium absorption of the diaphragm was completed, the apparent activity density of the titanium tritide source film samples was detected via tritium imaging method, which verified the reliability of the simulation model. The results show that the titanium tritide source films prepared by 500-2 600 nm have a tritium-to-titanium ratio of about 1.9, and the apparent activity density measured by tritium imaging is consistent with the simulation results. As the thickness of the source film increases, the peak of the electron emission energy spectrum on the surface shifts towards the high energy zone until close to 8 keV. It exhibits the phenomenon of “hardening”, which may be due to the fact that high-energy particles are more likely to penetrate the material and low-energy particles have a greater probability of being absorbed by the source film material. The increased thickness of the film leads to enhanced self-absorption effect, causing the waste of tritium source energy, and the apparent electron power tends to stabilize when the film thickness increases to about 1 000 nm. Therefore, the film thickness used should preferably not exceed 1 000 nm, aiming to avoid the waste of radioactive source. Titanium tritide source film with characteristic parameters (1 000 nm thick, T/Ti=1.9) has a total activity density of 519.5 mCi/cm², which theoretically provides an apparent activity density of 46.6 mCi/cm² and an electron emission power density of 2 243.9 nW/cm². Considering the decay effect of tritium, the source film with characteristic parameters can still provide an electron emission power density of about 1 000 nW/cm² for 15 years of using, which is about 44% of the initial power.