A two-dimensional microstrip gas chamber (MSGC) with a 5 cm x 5 cm detection area has been developed. It has 254 anodes and 255 back strips, both with 200 micro m pitches. Using this MSGC, linear polarization of X-rays was successfully measured in the energy range 6-14 keV. In addition, the performance of the MSGC as an X-ray imaging polarimeter has been simulated using the EGS4 program (Electron Gamma Shower, Version 4) modified for this purpose. In this article, the results of both the polarization measurement and the simulation are reported.