In this study, switching mechanism in all-optical Sagnac interferometer using semiconductor optical amplifier (SOA) is studied numerically. The switching characteristics of this scheme are investigated for picosecond input pulses. SOA all non-linear gain compression effects are considered altogether simultaneously in all-optical Sagnac interferometer switch (AOSIS). The effect of structural and input pulse parameters on the AOSIS operation are identified and analyzed. Simulation results show that some key parameters such as SOA unsaturated gain, control pulse energy and width, SOA length and loop asymmetry of this scheme should be selected (or designed) so that the best operating conditions for switching is satisfied. It was shown that control pulse characteristics have the most effect on switching operation. It was shown that effects of picosecond nonlinearities of SOA are very important on switching characteristics. Furthermore, use of picosecond input pulses caused to the improving switching windows shape and the increasing bandwidth which be useful for broadband applications.