The grinding-polishing machine is a double-disc desktop, applicable to pre-grinding, grinding and polishing of metallographic sample. The machine is an indispensable equipment in making the metallographic sample. The machine has a cooling device to cool the sample during pre-grinding, thus preventing the damage of the metallographic structure caused by overheat of the sample. Its left disc is a grinding disc, and its right disc a polishing disc, operated by two people simultaneously. The machine, easy to use, safe and reliable, is an ideal preparation equipment for the labs of plants, research institutes and universities and colleges.