Since the thin-disc laser is proposed in the 1990 s, it has been widely considered as a sort of high power light source. Compared with the traditional solid-state laser, the thin-disc laser works in a very thin sheet, so it can significantly reduce the thermal effect of the crystal, and has the advantages of excellent beam quality, high conversion efficiency, and high output power and so on. An overview of the principle of the thin-disc laser is provid.ed, its key technologies and the applications such as industrial, military and scientific research are summarized, andits future development is forecasted.