The diode laser side pumped 1kHz E-O Q-switched TEM00 mode laser was studied in this paper. The single pulse energy of laser is 0.712mJ and 10ns pulse width. Using three type cooling Nd:YAG slab in the experiment, thermal effect in diode pumped Nd:YAG slab affect laser efficiency in high repetition rates operation of laser. The results obtained in this paper are applicable to the design of high-power diode laser pumped laser system.