With Cr⁴⁺∶YAG as the Q-switch and LDA end-pumped Nd∶YAG crystal, the passively Q-switched laser is composed. The 1.06 μm pulse laser output of 25 mJ、~6 ns and 24 mJ、~15 ns are obtained in 2 different designs of flat-flat cavity (output couple reflectivity R=35%) and flat-concave cavity (output couple reflectivity R=23%) respectively. The experiment results are in good agreement with the theoretical data of passively Q-switched laser output. In another experiment, the pulse interval accuracy of the 20 Hz passively Q-switched laser in the temperature range of -40 ℃~+50 ℃ is measured. In this temperature range, the pulse interval accuracy is less than ±2.8 μs. Finally, according to the above experimental results, in order to meet the requirements of laser designator for the use of laser sources, some optimization ideas for the laser design areproposed.