Microbial electrolysis cells (MECs) are important for environment and renewable energy source. They were used for bio-hydrogen production by bacteria from organic matters, which is biological method to treat wastewater. Therefore,in this studyMEC was used for bio-hydrogen producing by two bacterial strains: Escherichia coli NRRL B-3008 and  Pseudomonas  aeruginosa  ATCC 27853 in MEC 1 (300ml), MEC 2 (400ml) and MEC 3 (500ml)were applied from domestic wastewater. Volumes of MEC refer to anode chamber. Applied voltage of 0.4V, 0.6V and 0.8V was used as an external electrical circuit in MECs (1, 2 & 3). The lowest value of Bio-Hydrogen production rate (Bio-HPR) 112.28 cm³ was obtained by domestic wastewater without bacteria in MEC 3 (500ml) at applied voltage 0.8V. While highest values of Bio-HPR 235.87 and 268.08 cm³ were obtained by E. coli NRRL B-3008 and P. aeruginosa ATCC 27853 in MEC 3 (500ml) at applied voltage 0.8V from domestic wastewater respectively.