A diode-pumped passively Q-switched Nd:YLF laser was demonstrated by using saturable absorber of Cr4+:YAG. At the incident power of 7.74 W, pure passively Q-switched laser with per pulse energy of 210 'mu'J and pulse width of 19.6 ns at repetition rate of 1.78 kHz was obtained by using Cr4+:YAG with