A compact Nd:YAG nanosecond laser passively Q-switched by Cr4+:YAG crystal with the operation repetition tunable from 1 Hz to 10 Hz is reported. Type II phase match crystal of KTP is adopted for the frequency doubling to obtain the stable output of 532 nm laser pulse. The single laser pulse energy of 1 064 nm is approximately 800 mJ and the laser pulse width is around 7 ns. The output energy of 532 nm exceeds 500 mJ, and the average pulse energy at different operation repetition are given as 551 mJ@1 Hz, 553 mJ@3 Hz, 546 mJ@5 Hz and 518 mJ@10 Hz, respectively. The RMS of 532 nm laser pulse energy is less than 6.2%. When the laser beam is injected onto a ground glass of 20 cm, the spot image is measured by a scientific-level CCD. The result shows that the second-order quantum correlation function g(2) value of the pseudo-thermal light is 1.963, close to the theoretical value of 2. The laser system promises the improvement of Ghost imaging quality.