Abstract. A significant degree of the astrophysical X-ray sources are expected to emit linearly polarized radiation. Measurement of the angle and degree of polarization can provide information of emission processes, geometry and magnetic field of the observed source. The standard techniques used to measure polarization are Bragg Diffraction and Thomson Scattering which have limitations such as narrow energy band sensitivity, high background etc. The technique discussed here is based on Photoelectric Effect which makes use of the emission direction of the photoelectron to measure the polarization angle. This is experimentally done by using GEM (Gas Electron Multiplication) detector. GEM amplifies the primary ionization leading to easier read out of the track of the photoelectron and hence the reconstruction. Operating parameters of GEM detector such as gas-mixture, pressure, absorption thickness and electric field decide the track length and the diffusion of secondary electrons which in turn defines the accuracy of the reconstruction. In addition, these parameters also decide the sensitivity and the detection efficiency of the detector. Garfield, a simulation tool is used in the present work to optimize these parameters of the GEM detector. Here we discuss the results pertaining to the photoelectron track length w.r.t gas mixture and pressure. These results will also be discussed in perspective of diffusion and sensitivity.