Abstract: A prototype of the readout electronics system was designed for the external experiment in HIRFL-CSR. This system is responsible for the readout of the TOF wall detector, the neutron wall detector and the MWDC. The time measurement was based on leading edge discrimination, while the TOT method was employed in charge measurement, and this made the time-walk to be corrected. The electronics was designed based on the PXI standard in order to guarantee that this system has a high data transfer rate and a good flexibility. The laboratory tests and preliminary commissioning tests with the detectors were conducted, which indicate the system functions are good.