A high quality single crystal of Cr4+:YAG, grown in our laboratory by the Czochralski method was used in the Q-switching experiment successfully for a Nd:YAG laser, which provided laser pulses of 800 ns in duration, a repetition rate of 3～13.33 kHz and an average pulsed output power higher than 13 W. The jitter of the Q-switched laser is also discussed in this paper. A possible mechanism was suggested and indicated that a more stable output of Cr4+ :YAG Q-switched laser would be achieved by further improving the crystal qulity in the growth and post-treatment processes.