In order to solve the problem of low tuning accuracy in wavelength switchable fiber laser, an erbium-doped fiber laser based on all fiber taper interference filter structure is proposed and designed. The fiber Mach-Zehnder(MZ) interference structure is fabricated by melting the multimode fiber with a fusion splicer. The periodic energy distribution is used to realize the wavelength flexibility of erbium-doped fiber laser tunable output. The experimental results show that the period of the fiber filter is 0.8 nm, the laser operating threshold is 58 mW, the single wavelength tunable laser output is realized in the L-band of 1573.45~1574.59 nm, and the minimum wavelength interval is 0.11 nm; the dual wavelength laser switchable output is realized by adjusting the polarization controller. In the 10 min stability test, there is no obvious wavelength drift.