Molybdenum diselenide (MoSe2) nanosheets are coated on the tapered region of microfiber (MF) to achieve active light control by light with order of mW. The MoSe2 nanosheets are illuminated by 405 nm and 980 nm lasers which change the conductivity of the MoSe2, thus the transmitted power of the guiding light (λ = 1550 nm) within the MF can be controlled. The transmitted optical power of the MF has a relative variation of ~2 dB (0.165 dB/mW) when the 405 nm light is illuminating on the MoSe2 nanosheets with a power ranging from 0 to 11.6 mW. The sensitivities of the 980 nm in-fiber and out-fiber experiments are 0.092 dB/mW and 0.851 dB/mW, respectively. The rise and fall times of the transient response are 0.4s and 0.6s, respectively. Therefore, the guiding light in our MF coated with MoSe2 can be effectively manipulated by the 405 and 980 nm light (order of mW). The MF coated with MoSe2 has potential applications in light sensing and all-optically controllable devices.