We designed a soft x-ray photo-electron spectrometer(PES) for diagnosis of plasma electron temperature in tokamak. PES analzes x-ray energy using photo-electric effect in carbon target. We investigated the characteristics of spectrometer theoretically, the investigation revealed that PES can analyze x-ray energy from 30 eV to 2 keV, that the space resolution is 1 cm and $\pm15^\circ$ vertically, that the time resolution is 1 ms and that PES can measure electron temperature from 50 eV.