Abstract: A novel Micro-Strip Gas Chamber （MSGC） was fabricated on the CVD diamond film/Si composite substrate, with anode width of 7μ m, cathode width of 100μ m and pitch of 200μ m. At room temperature and 1.01× 10⁵Pa, 5.9 keV X-rays from a ⁵⁵Fe source were used to measure the pulse height distributions of the MSGC operating at different high voltages and Ar+ CH₄ gas proportions. The results show that MSGC has a high ratio of signal to noise. The energy resolution depending on high voltage and gas proportion was discussed in detail. On the optimum condition of Ar+ 10% CH₄ gas mixture,-1100V drift potential and-650V cathode voltage, a better energy resolution of 12.2% is achieved.