The Low frequency oscillations (LFOs) have an effect on small signal stability of power system. As power system started to operate near the stability limits , it will be lead to system instability. Power system stabilizers (PSSs) are provided with automatic voltage regulator to damp effects of LFOs. This paper studies the effect of interval type-2 fuzzy logic power system stabilizer (IT2FLPSS) on the stability enhancements of a single machine power system connected to the infinite bus. A conventional power system stabilizer (CPSS) has been introduced, as well as controller based on interval type-2 fuzzy logic (IT2FL) is proposed to be used in PSS technique. MATLAB/SIMULINK program is proposed to compare between CPSS and IT2FLPSS by using different disturbance scenarios.