In this paper, simulation of a gas micro-strip detector by using the MCNPX code, the feasibility of alpha spectroscopy for radon and its progeny has been investigated. Initially, for the verification of the code, the range of alpha particles released from ²²²Rn gas in the air has been obtained in the standard condition, which is consistent with the experimental results. Subsequently, the energy loss per unit path length, range of alpha particles and radon progeny was measured, then the relationship between the range, the energy and the air pressure has been achieved. Finally, the simulation results have been compared with the results of the particle range relationship, pressure and energy, and the radon spectroscopy has been performed with the studied detector. The comparison of the spectrum obtained with the simulated micro-strip detector and the experimental results shows that the introduced micro-strip detector, in addition to the ability to measure radon and daughters, also has the ability to extract the spectrum from it.