Laser diode (LD) pumped Nd:YAG laser is widely used in precise manufacture. A kind of simplified LD side pumped acousto-optic Q-switched Nd:YAG laser used for Al2O3 ceramic wafer micro drilling is described. The taper of the hole in Al2O3 ceramic wafer is reduced effectively when the laser beam quality is optimized by modifying the resonator structure. The TEM00-mode output power is above 20 W and the pulse width is about 200 ns when the laser is working at 10 kHz. And the M2 factor of the beam is lower than 1.5 in each direction.