High power sub-nanosecond electrical pulse system based on photoconductive semiconductor switch (PCSS) is reported. To get high power sub-nanosecond electrical pulse, experiments of three kinds of switches such as a lateral semi-insulating GaAs PCSS, gas gap added into the two electrodes of the switch on the GaAs chip and combinatorial switchs of GaAs PCSS with gas switch are triggered by nano-second laser pulse. The source of the triggered laser is YAG lasers, and the width of the laser is about 3.5 ns. A maximum current is only 38A by a single 3.5mm PCSS. The combinatorial switch of a 3mm-gap PCSS and a 0.6 similar to 0.8mm gas switch is triggered at the biased voltage 4000V, a high current pulse is acquired with the peak value above 5160A, and ns risetime. The voltage transmission efficiency is more than 100%(129%),which can not be answered for the ohm-theorem. This phenomena is explained with the theorem of plasma.