The ion source is the critical part of Experimental Advanced Superconducting Tokamak (EAST) neutral beam injection (NBI) system. Two ion sources are equipped in one beam line. The voltage and current signals of grids are the important diagnostic data in the duration of beam extraction, especially the rising and sparking edge. In order to achieve the functions of data acquisition and isolation transmission, the first prototype of high-speed data acquisition system of ion source has been developed. The system contains the advantages of 40 MS/s sampling rate, 8-bits resolution and optical isolation transmission. Field programmable gate array (FPGA) is used as the control chip in the system. The system has been tested for the voltage of plasma grid (PG) and the beam current. The error range of system is < 3% after the test. These results present that the data acquisition system is promising equipment for NBI.