This paper reports the design of the first extracting mirror of SR (synchrotron radiation) monitor system in SSRF (Shanghai SR Facility). The design aims at extracting the visible light from synchrotron radiation without distortion. The difficulty is that the high power X-ray of SR heats and damages the extracting facility

then it is transfigured to affect the wavefront and amplitude of the visible light. After the analysis of SR power spectrum and the heat transfiguration based on ANSYS program

we designed a beryllium mirror with a water-cooling system to reflect visible light and transmit X-ray to satisfy requirements of design.