A tunable erbium-doped fiber laser (EDFL) is proposed and demonstrated experimentally. It is based on a tunable fiber filter using the pump induced refractive index change characteristics of the ErYb codoped phosphosilicate fiber (EYDF) based modal interferometer (MI). The laser achieves a tunability of 2.39nm and 1.60nm, with the wavelength linearly tuned from 1534.05nm to 1536.44nm and from 1554.36nm to 1555.96nm by changing the pump power injected into the MI. Its side mode suppression ratios are 30dB and 33dB, respectively. The stability of the tunable EDFL is getting better with the continuous improvement of the power of pump 1, and the dual-wavelength power fluctuations are less than 0.22dB and 0.12dB within 20 min at 250mW of pump 1, respectively.