Abstract: Multi-Wire gaseous detectors have been widely used in the fields of nuclear physics and nuclear technology since they have the advantages of radiation hardness, fast response, large sensitive area, low cost and convenient fabrication. First, the electric field calculation theories for multi-wire gaseous detectors were introduced, and then the electric field calculations and the structure design for the drift region and avalanche region of a multi-wire gaseous detector had been carried out with ANSYS and GARFIELD. Next, the designed detector had been simulated in the case of cosmic ray irradiation with GEANT4, and the output results of current pulses, voltage pulses, the integrated charge for each event and the overall statistic results of the integrated charge were obtained. Furthermore, the multi-wire gaseous detector had been built and was used to measure the cosmic rays. The experiment results agree well with the previous simulation results. The simulation methods and the related experiment technologies in this study can be used to do design optimizations and experiment evaluations for gaseous detectors.