The influence of heat effect produced by gain medium and electro-optic crystal working at high repetition rate on a regenerative amplifier is investigated in this paper. Depolarization loss induced by heat generated in Nd∶YAG crystal and thermal absorption of KD*P electro-optic crystal were measured,and a compensating element to compensate the loss of thermal depolarization was used effectively. A BBO Pockel cell for regenerative amplifier was designed by ourself,and effective amplification is obtained. An output pulse energy at 1064 nm is obtained from the picosecond laser pulse regenerative amplifier by laser diode (LD) side-pumped with 3 mJ each pulse and amplification radio of 3×106 at 1 kHz repetition rate.