Abstract: In order to improve conversion efficiency and output energy of a picosecond optical parametric generator/amplifier (OPG/OPA), walk-off compensation structure and special design of lens film system were used to verify the experiment. The evolution of beam quality M² of OPA signal light at different pumping energies and the tuning output performance of OPA signal light ranging from 430nm to 680nm were studied. The results show that, when pumped by 6.9mJ at 355nm, maximum output energy of 2.7mJ at 510nm signal is obtained. The corresponding optical-optical conversion efficiency is 39.1%. Photon conversion efficiency is 56.2%. This method can effectively improve output energy and conversion efficiency of OPG/OPA. This study is helpful for the characterization of ultraviolet and deep ultraviolet crystals.