A Q switched Nd:YAG laser end pumped by a QCW 600 W laser diode array(LDA) is reported.Coupling system of the laser are micro cylindrical lens array and lens duct,which are made by us.Using Cr 4+ :YAG as Q switch and selecting right length of the Nd:YAG crystal,we get short cavity length.Distribution of multi pulse figure on time and space when the Q switched laser has a short cavity are researched in our experiment.A single spike output of each pumping is obtained with plane plane cavity structure and 11 mm cavity length.The pulse width is <4 ns and pulse energy is 4.5 mJ.