An optical communication system based on the pulsed laser with GHz-repetition-rate and multi-wavelength enable an increase in data transmission rate and data capacity. We propose a novel hybrid cavity with single-mode fiber, multi-mode fiber and single-mode fiber (SMF-MMF-SMF) configuration for GHz ultrafast laser with multi-wavelength. The length of each section is elaborately designed to reduce the transmission loss between the SMF and MMF, as well as to limit its total lengths under 10 cm. By adopting the proposed hybrid cavity, the >1 GHz-repetition-rate fiber laser operation with 4 wavelength peaks was demonstrated, showing a signal-to-noise of 90 dB. Furthermore, great tunability in spectra by manipulating the launched cavity parameters was also proved. To the best of our knowledge, this is the first realization of multi-wavelength among the GHz lasers using the SMF-MMF-SMF cavity architecture. The finding might provide new opportunity for large capacity high-speed optical communication system.