The diagnostic unit of pulsed xenon lamp transient discharge current is an important part of the energy system in an Inertial Confinement Fusion(ICF) laser device. Based on the analysis of problems such as strong electromagnetic interference, noise coupling, and topological constraints of multiple parallel acquisition circuits, a design method of multi-level isolation and Field Programmable Gate Array(FPGA)-based multi-channel synchronous parallel architecture is proposed and the prototype is developed. Experiments show that the current measurement range of the diagnostic unit is 0-25 kA, the sampling rate is 200 kHz, and the measurement accuracy is better than ±0.5%. This design meets the requirements of synchronous diagnosis of the discharge current of 20 pulsed xenon lamps under 31 kV of working point voltage. Compared with traditional design, this method has stronger electromagnetic compatibility and higher integration of parallel acquisition design.