In this paper the evaluation & performance analysis of an interval type-2 fuzzy logic controller (IT2 FLC) as a power system stabilizer (PSS) is carried out. The single machine infinite bus (SMIB) system is considered for evaluation and implementation of IT2 FLC as PSS. The input signals to the controller are considered as speed deviation & acceleration. The evaluation of the controller is considered with 20 separate types of membership functions (MFs) and treated as IT2 FPSS on SMIB system to evaluate the performance of each. The performance of these MFs is evaluated graphically as well as in terms of ISE, IAE & ITAE as the performance index. The better suitable MF as FPSS is decided out of considered 20 MFs. The selected MF based IT2 FPSS is tested for small signal performance analysis of an SMIB system with wide operating conditions of a power system. The performance with IT2 FPSS is compared to the performance of the power system without PSS & with conventional PSS.