A high repetition rate all-fiber picosecond laser which mode-lacked by a semiconductor saturable absorber mirror is demonstrated. Stable mode-locked pulse train is obtained when the pump power is 112 mW in the ring cavity. The pulse width of the output laser is 4.2 ps at the repetition rate of 19.2 MHz, and it exhibits a spectral bandwidth of 3.6 nm at the center wavelength of 1 064.1 nm. Due to the length of the cavity, it is difficult to increase the repetition rate of the fiber laser. So a novel low-loss high-repetition-rate pulsed laser modulator based on optical coupler and time delay fiber is introduced to increase the repetition rate of the seed to 1.2 GHz. This design effectively reduces the energy loss of the pulse during coupling, which provides a new way to boost the repetition rate of the all-fiber ultra-short pulsed laser.