A switchable multi-wavelength erbium-doped fiber laser based on a microfiber Sagnac loop is proposed and experimentally demonstrated. The microfiber Sagnac loop comb filter is fabricated by inserting a 5.5 cm polarization maintaining fiber between two outputs of an optical microfiber coupler with a waist diameter of 5.68 $\mathrm{\mu }\mathrm{m}$. The filter is fused into the fiber ring cavity and the four-wavelength output laser is realized by adjusting the polarization controller. In addition， the output of single-， dual-， triple- wavelength laser can be switched， and the outputs interval of dual-， triple-wavelength are tunable. The experimental results show that the 3 dB linewidths of laser output spectra are less than 0.027 nm and the side-mode suppression ratio are more than 40 dB， up to 58 dB. When the fiber laser operates at triple-wavelength， the wavelength shift and peak power fluctuation are within 0.028 nm and 0.9 dB in one hour. The laser has stable output and good monochromaticity， which can be applied in fields of wavelength division multiplexing and all-optical communication systems.