A two-dimensional multi-wire proportional chamber detector based on 3He gas is developed for meeting the multifunctional reflection spectrum detection requirements of China Spallation Neutron Source (CSNS). Based on the previous researches in our laboratory, three different wire structures are studied for optimizing the wire readout structure of the two-dimensional multi-wire proportional chamber detector, and the performances of the detectors are measured by two readout methods:the center of gravity readout method and the digital readout method in this paper. The selected method could satisfy the requirement of multifunctional reflection spectrum instrument. Finally, the results indicate that the position resolution and the imaging capability obtained by using the center of gravity readout method should be better than by using the digital readout method. The position resolution could reach to about 160 m by using the center of gravity readout method. While the position resolution of the detector could be obtained to be about 400 m by using the digital readout method. Re-designed and compared with each other are the three different wire structures:1.5 mm of the anode wire pitch and 4 mm of the readout strip pitch with the center of gravity readout method, 1.5 mm of the anode wire pitch and 2 mm of the readout strip pitch with the digital readout method. Both of the optimized designs of the wire structure could meet the requirement of the position resolution for the reflection spectrum device.