The grinding-polishing machine is a double-disc desktop, applicable to rough grinding, accurate grinding and polishing of metallographic sample. The machine has two-step constant speed of 300rpm and 600rpm, thus widening its application. The machine is an indispensable equipment in making the metallographic sample. The machine has a cooling device to cool the sample during grinding and polishing, thus preventing the damage of the metallographic structure caused by overheat of the sample. The machine, easy to use, safe and reliable, is an ideal sample preparation equipment for the labs of plants, research institutes and universities and colleges.