Amorphous Fe-Co-B nano-sized magnetic particles were prepared and firstly introduced into Ga(91.6)Sn(8.4)alloy to fabricate liquid metal-based ferrofluids. The Fe-Co-B particles are amorphous and spherical with an average particle size of 10.6 nm. The saturation magnetization of amorphous Fe-Co-B nanoparticles after annealing treatment at 550 degrees C is 81 emu/g, which is higher than that of Fe-Co-B nanoparticles without and after annealing treatment at 450 degrees C. The annealed Ga(91.6)Sn(8.4)alloy-based ferrofluids with amorphous Fe-Co-B nanoparticles exhibit high stability, which is superparamagnetic with a saturation magnetization of 2.57 emu/g. Besides, the Ga(91.6)Sn(8.4)alloy-based ferrofluids show temperature-sensitive magnetic property. The magnetoviscous property demonstrates that the annealed Ga(91.6)Sn(8.4)alloy-based ferrofluids show relatively strong magnetic responsiveness. The hysteresis curves of viscosity-magnetic field show the annealed Ga(91.6)Sn(8.4)alloy-based ferrofluids have superior reversibility and exhibit a desirable high-temperature performance.