This invention is a kind of electrooptic Q-switch element made of a single crystal and belongs to the application of crystal in electrooptic technology field. The invention consists of electrooptic Q-switch which is made of La.sub.3Ga.sub.5SiO.sub.14 or Nd:La.sub.3Ga.sub.5SiO.sub.14 or the other related crystal materials such as La.sub.3Ga.sub.5-xAl.sub.xSiO.sub.14, Sr.sub.3Ga.sub.2Ge.sub.4SiO.sub.14, Na.sub.2CaGe.sub.6O.sub.14, Ca.sub.3Ga.sub.2Ge.sub.4O.sub.14, La.sub.3Ga.sub.5.5Nb.sub.0.5O.sub.14 and La.sub.3Ga.sub.5.5Ta.sub.0.5O.sub.14 with the common shape or a specific shape containing Brewster angle as shown in figure. This kind of electrooptic Q-switch can be used in YAG laser and other laser. It overcomes the shortages of the commercial Q-switches, such as the high, un-adjustable, low stable half-wave voltage and great half-wave voltage variation with temperature. The advantage of this kind of electrooptic Q-switch is its low, adjustable, high stable half-wave voltage.