Abstract: In order to improve the amplification efficiency of high repetition frequency Nd:YVO₄ laser, a new method of double-pass amplification for the uniaxial crystal like Nd:YVO₄ was introduced. The Faraday isolator and Nd:YVO₄ was placed with a rotation angle of 45°, and this method could be applied to keep the polarization direction of the seed laser in parallel with the Nd:YVO₄ c-axis. The simulation results show that the seed laser with 1W average power could be amplified to 36.2W in this double-pass amplification, and the amplification factor was improved 41.5% corresponding to a amplification method consisted with a polarizer and a quarter wave plate. This study is very important for laser amplify of weak seeds with Nd:YVO₄ as laser amplification.