Inappropriate effects of fossil fuels and conventional power generation systems on the environment as well as the growing interests in renewable energy systems have necessitated a sustainable energy system for the next decade. Hydrogen is the one of known new energy fuel for sustainability that could generate by PEM electrolyzer. The present study was aimed at optimization of functional parameters of PEM electrolyzer by energy and exergy analysis. For this, we have developed a electrochemical- mechanical model by MATLAB and analyze the energy and exergy efficiency. The results revealed that increased of pressure and temperature cause to close the exergy efficiency to energy efficiency and improve the system performance. The optimal pressure and temperature respectively are 3 atm and 273 K. Also, the voltage of system are raised by increasing the current density.