A high average power and high beam quality picosecond laser system combined with diode-end-pumped Nd∶YVO4 and laser diode-side-pumped Nd∶YAG amplifier is described. The system combines the advantages of Nd∶YVO4 crystal having large stimulated-emission cross section and Nd∶YAG crystal having good thermal conductivity. The diode-end-pumped Nd∶YVO4 amplifier allows the laser from the oscillator to obtain high gain so that the laser can amplify rapidly and the diode-side-pumped Nd∶YAG amplifier benefits to obtain high output power. The Nd∶YAG amplifier is designed as double-pass form to increase the efficiency of the amplifier. Spatial filters are adopted between amplifiers to ensure good beam quality and mode matching. Picosecond laser with average power of 43.4 W and good beam quality factor M2<1.7 is generated from this laser system.