A wavelength tunable, passively mode-locked Yb-doped double-clad fiber laser with a birefringent filter is demonstrated in this paper. By carefully rotating the filter, the central wavelength of the mode-locked fiber laser can be continuously tuned from 1063.9 nm to 1091.1 nm. The pulse duration ranges from 13.9 ps to 16.8 ps, and spectrum width varies between 15.8 nm and 18 nm. The maximum average output power of 212 mW is obtained at the central wavelength of 1063.9 nm. The corresponding pulse energy is 8.5 nJ. A theoretical model is established based on the coupled Ginzburg-Landau equations and Jones matrices. Simulation results agree with the experimental results.