A special readout electronic system was developed to meet the needs of the ³He multiwire proportional chamber detector (MWPC) of multi-functional reflectance spectrometer (MR) of China Spallation Neutron Source (CSNS) . The system is mainly composed of core preamplifier board and trigger fan out board. Six preamplifier boards are used to digitize 142 analog signals of the detector. The neutron information is screened through the discrimination mechanism, and the effective neutron cases are packaged and sent to the back end. The trigger fan out board provides the T0 signal and trigger signal arriving at the same time to ensure the alignment of data. The readout electronics system has been tested in laboratory and beam conditions respectively. The test results show that the performance is better than the design requirements. At present, the MWPC detector has been successfully installed in the field of MR spectrometer, and has begun to operate stably.