Power system stabilizers have been widely used in generation systems to enhance the transient stability of the power system. Low frequency oscillation may occur as a result of excitation system which exerts a phase lag. Conventional power system stabilizers using a lead-lag controller have been used in utility for decades. Proper tunning of the parameters of stabilizer is essential for effectiveness of stabilizer. Many optimization techniques have been proposed for finding the optimum parameters of stabilizer. In this paper tuning of parameters of a Conventional Power System Stabilizer in a Single Machine Infinite Bus (SMIB) using Genetic Algorithm (GA) is proposed. The power system is modelled in Power Factory and the optimization is done through MATLAB optimization toolbox. The cost function is to maximize the damping ratio which is calculated using Power Factory Modal Analysis. Using DIgSILENT Programming Language (DPL), a real time data exchange between MATLAB and Power factory is set during optimization process. The result of simulation proves the effectiveness of optimization process.