Silicate-clad heavily Yb3+ doped phosphate core multimaterial fiber (MF) was successfully drawn by using a molten core method, which has a high gain per unit length of 5.44 dB/cm at 1.06 µm. What is more, an all-fiber-integrated passively mode-locked fiber laser based on a 5 cm long MF was built. The mode-locked pulses operate at 1055 nm with a period of ∼555ps, and the fundamental repetition rate is 1.787 GHz. For the first time, to the best of our knowledge, we demonstrate the realization of a mode-locked fiber laser with a gigahertz fundamental repetition rate based on a silicate-clad heavily Yb3+ doped phosphate core MF.