Focusing the TEA CO2 laser pulse onto a metal target in the vacuum cell, the backward jet of plasma produced by laser pulse can create electric pulse between target and cellwall. The effects of beam focusing and vacuum condition on the conversion are investigated experimentally. The maximum output voltage is 300 V when the peak power density of laser pulse is 1.4x109 W/cm2. Over-all efficiency is 0.01%. Using two separated collecting electrodes, the velocity of plasma expansion can be obtained.