To make full use of the long pump time of krypton fluoride excimer laser amplifiers and to increase the amplification efficiency, we carried out experimental research on multi-pulse amplification and beam combination of ultra-short UV pulses. The effect of delay time on pulse energy was studied using dual pulse amplification. Based on the above relationship, optimal delay time was confirmed, the increase of total energy and the reduction of amplified spontaneous emission (ASE) were both archived. Amplification of four ultraviolet pulses was achieved, and the energy was nearly four times that of the single pulse amplification. We also explored beam combining technology of ultraviolet ultra-short laser pulses, and combined two sub-picosecond pulses accurately.