Abstract: An all-fiber switchable multi-wavelength erbium fiber laser was proposed in this paper. A sinusoidal phase modulator composed of a piece of single-mode fiber around a piezoelectric transducer was inserted in the ring cavity, combined with an all-fiber Mach-Zehnder interferometer based on cascade in-line two-taper as the comb filter, which suppressed the mode competition owing to the homogeneous broaden line in erbium-doped fiber and eliminated the unstable wavelength lasing. Simultaneous and stable five-wavelength lasing was observed with 0.804 nm intervals at room temperature. The signal to noise ratio is higher than 40 dB, the 3 dB bandwidth is about 0.023 nm, and the five lasing lines in power differences are less than 14 dB. Meanwhile, the laser has highly flexible wavelength switchable property. By adjusting the driving signal and polarization controller, single wavelength lasing output, switchable dual, triple and ever more wavelengths lasing output could be realized. These advantages enable this laser as a potential candidate for high-capacity wavelength division multiplexing systems and mechanical sensors.