The electrical properties of stabilized amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. Carrier mobility was measured using time-of-flight (TOF) measurements to investigate the transport properties of holes and electrons in stabilized a-Se film. A laser beam with pulse duration of 5 ns and wavelength of 350nm was illuminated on the surface of a-Se with thickness of 400 $mu extrm{m}$. The photo induced signals of a-Se film as a function of time were measured. The measured transit times of hole and electron were about 8.73${mu} extrm{s}$ and 229.17${mu} extrm{s}$, respectively. The hole and electron drift mobilities decreases with increase of electric field up to 4V/$mu extrm{m}$. Above 4V/$mu extrm{m}$, the measured drift mobilities exhibited no observable dependence with respect to electric field. The experimental results showed that the hole and electron drifting mobility were 0.04584 $ extrm{cm}^2$ V$^$-1/s$^$-1/ sand 0.00174 $ extrm{cm}^2$V$^$-1/s$^$-1/ at 10 V/$mu extrm{m}$.