Compress of the beam in unstable resonators by prism pair is discussed theoretically. A pair of prisms are placed into an electro-optical Q-switch Nd:YVO₄ slab laser with an unstable-stable hybrid resonator. The beam is compressed in the unstable direction, which reduces the dimension of electro-optical crystal BBO and remains the large mode volume in the laser crystal. It fits high power performance. With CW pump power of 66 W, average power of pulse laser is 3.6 W at 2 kHz repetition rate, 1.8 mJ per pulse. Pulse width is 6ns. The experiment indicates that the laser can output high repetition rate and high intensity pulse with good beam quality, when the pair of prisms is in the resonator.