To high power laser driver, the disk amplifiers are the most important sources of energy and power. The energy transmission and conversion in high power laser disk amplifier are discussed. The energy transmission is achieved by the energy bank modules, pulse flash-lamp, pump cavity and gain medium. The effects of different energy transmission process on the whole performance of disk amplifiers are researched by simulation and experiments. Results show that the small signal gain coefficient of 5.0%cm-1 and energy storage efficiency of about 3.0% are achieved by primary optimization in technical integration line (TIL). But because of the quality of some key elements, the best results are not obtained. High efficiency does not only improves the disk amplifier performance, reduce the cost, but also improves the amplifier reliability and stability.