The fundamental characteristics of laser cutting for thin copper plate by a Q-switched single-mode fiber laser were experimentally investigated, and the effects of the nozzle shape on cutting results are also discussed. In the case of traditional convergent nozzle with nitrogen assist gas, it was impossible to cut under any experiment condition, since assist gas pressure on workpiece was lower. On the other hand, high speed cutting of 30mm/s could be carried out using high-performance Nozzle Laval 800 and Nozzle Laval 800 IEZ, since high assist gas pressure could be supplied on the workpiece. In addition, the dross height using Nozzle Laval 800 and Nozzle Laval 800 IEZ was very small less than 10um, and the very narrow kerf and straight cut shape could be obtained. Therefore Q-switched single-mode fiber laser with high-performance nozzles proved to be useful for cutting of thin copper plate.