To use for GEKKO XII Module glass laser system, we have developed an oscillator system, which consists of a mode-locked YAG laser, a pulse selector, a pulse shaper, and controller circuits. The mode-locked YAG laser oscillates at a wavelength of 1.052μm and gives out-put energy of 10 μJ/pulse. The pulse width is variable in a range from 90ps to 1.4ns. The pulse selector switches out a single pulse from a mode-locked pulse train with 50% transmittance. The ratio of the energy of the selected pulse to that of the unselected prepalses is greater than 108. The pulse shaper is of a passive type. It produces a shaped pulse whose envelope is determined by the requirements for target compression experiments.