Abstract: C-Ti granular films with different thickness were prepared, acting as the cathode emission film, to study the influence of granular film thickness on electron emission characteristics. When symmetric triangular wave voltages of different magnitudes are applied to the prepared cathode device, electrical formation is then carried out to the devices. It is shown that the turn-on voltage of the 69 nm-thick-film equipped device is 32 V, with the emission efficiency reaching its maximum at 33 V, while the turn-on voltage of the 855 nm-thick-film equipped device was 23 V, with the maximum emission efficiency appearing at 23 V. It is also illustrated that the 855 nm-thick-film device has a much wider voltage range and a much higher electron emission efficiency than the 69 nm-thick-film one.