PLZT electro-optic (EO) ceramic has good transparency and high EO effect. It has many advantages for realizing the all-fiber Q-switch. The principle of Q-switch based on PLZT was analyzed. And the time distribution of the Q-switch was measured. An all fiber single-mode actively Q-switched ytterbium-doped ring fiber laser based on PLZT switch was studied in experiment. The peak power, pulse width, spectral width and pulse energy of the Q-switched pulse are 25.6 W, 80 ns, 1 nm and 2.0 μJ respectively. At the same time, the effect of the pump power and repetition rate on pulse width and peak power was presented. The results show that the peak power of the pulse increases with the pump power and the pulse width decreases at the same repetition rate, and the pulse width increases with the repetition rate and the peak power decreases at the same pump power.