Broadband light amplitude tuning characteristics are demonstrated in a 2-D tin diselenide (SnSe2) nanosheets coated microfiber (MF) structure (SnSe2CMF). Due to the strong absorption characteristics of SnSe2 in broadband wavelengths, the transmitted optical power (TOP) of SnSe2CMF can be tuned by external pump lights with different wavelengths (405, 532, and 660 nm) over a broadband spectrum (1520–1620 nm). Five wavelengths are extracted in order to investigate the tuning performance. The TOP of SnSe2CMF increases with the pump light power and a maximum tuning efficiency of ∼0.3074 dB/mW is achieved. In terms of tuning speed, the minimum response time is ∼3.7/3.9 ms. The experimental results have qualitatively good agreement with the simulations predicted by FEM models. The demonstrated structure has the advantages of broad tuning bandwidth and high tuning efficiency. Therefore, it might be a promising candidate for building high performance broadband fiber-optic sensors and modulators.