We investigate the lasing characteristics of a laser-diode-array side-pumped electro-optic Q-switched Nd: Y3Al5 O12 ceramic laser operating at 1000 Hz pulse repetition rate. Using a YAG polycrystalline rod with Nd3+ concentration of 1 at.% as the gain medium, pumping with 808nm laser-diode-arrays, the Q-switched laser output at 1064nm wavelength with 23mJ pulse energy and less than 12ns FWHM pulse width are obtained at a pumping power of about 400 W, the slope efficiency is around 15%, the output beam divergence angle is about 1.2mrad.