The diode-pumped Nd∶YLF laser, using a plano-concave cavity,was reported by two pieces of Cr4 + ∶YAG passivelyQ-Switched crystal, and the output laserwavelength was 1053nm. Using a Cr4 + ∶YAG crystalwith a thick-ness of 0. 5mm and the small singal transmission of 90% , when the maximal pump powerwas17W, the output laser pulse width was 60. 6ns, the average output power was 1. 5W, the repetition frequency was 9. 5KHz, and a single pulse energy is 157. 9mJ; Using the other Cr4 + ∶YAG crystalwith a thickness of 0. 55mm and the small singal transmission of 95% , when themaximal pump powerwas17W, the output laser pulse width was 68. 6ns the average output powerwas 1. 35W, the repetition frequency was 14KHz, and a single pulse energy was96. 4mJ.