Abstract: In order to improve the output stability of LD pumpe d Nd:YAG laser Q-switched by Cr4+:YAG,the directional prism resonator is used,a single smooth laser pulse has been achieved with the energy stability changing from 7.3%~2.2%,pulse-width stability changing from 13.5%~6.5%,repetition rate stability changing from 0.01%~0.005%.The experimental result shows that compared with the plano-plane resonator,the directional prism resonator improves output stability of the laser greatly.It is reported for the first time that the directional prism resonator can eliminate the tail-pulse.