The object of this study is to design and analyze a Proportional-Integral (PI) control for SEPIC, which is the start-of-the-art DC-DC converter. The single Ended Primary Inductor converter performs the voltage conversion from positive source voltage to positive load voltage. This study proposes a development of PI control capable of providing the good static and dynamic performance compared to Proportional-Integral Derivative (PID) controller. Using state space average method derives the dynamic equations describing the SEPIC converter and PI control is designed. The simulation model of the SEPIC converter with its control circuit is implemented in MATLAB/SIMULINK. The PI control for SEPIC is tested for transient region, line changes, load changes, steady state region and also for components variations.