Today, transient stability studies constitute the major analytical approach to the study of power system electromechanical dynamic behavior. Transient stability study of a power system is required to determine whether the system will remain stable or not after major disturbances such as sudden load changes (induction motors starting), loss of generating units, transmission system faults or line switching. The degree of the system stability is an important factor in the planning of new facilities and interconnection. This study presents the transient stability analysis of Petroleum Development Oman (PDO) power system under three phase to ground fault, generator cutting, load cutting, three phase line switching and large motor starting. The analysis was carried out using the EDSA transient stability simulation program. The parameters of excitation systems and power system stabilizers were tuned to enhance the system stability. This study is very important as a step forward for the future project of interconnection the PDO power system with the power network of Ministry of Housing, Electricity & Water (MHEW (.