Our self-built dual-wavelength single-frequency fiber laser was used as a seed, and after being amplified by an acousto-optic modulator and multi-stage fiber, the laser was injected into a 100-meter long high nonlinear fiber with the zero-dispersion point of at 1550 nm. With the help of the four-wave mixing effect of the highly nonlinear fiber, a series of new spectral components were finally obtained under the pumping of the peak power of 13 W, and a total of 46 new spectra were generated in the range of 20 dB. These spectra spanned 1.337 THz and contained only one longitudinal mode in each spectrum. Since the new spectrum was generated based on the four-wave mixing effect, there was no gain competition between different spectra, so the multi-wavelength single- frequency of the laser can exist stably, and the spectral intensity was close to each other. The multi-wavelength single-frequency fiber laser not only has the advantages of a single-frequency fiber laser such as narrow linewidth, high coherence, and low noise, but also can simultaneously output multiple wavelengths of single-frequency lasers in an all-fiber structure, which makes it possible to have very important applications in the fields of multiplexing optical communication, optical frequency conversion, lidar, microwave photonics and so on.