An all-fiber dissipative-soliton passively mode-locked fiber laser is reported. A filter based on multimode interference is used, which consists of two seqments of single-mode fiber (SMF) and a segment of multimode fiber (MMF). By proper selection of the MMF length, a band-pass filter with central wavelength of 1067 nm and band width of 7.5 nm is fabricated. The filter for spectral filtering in an all-normal dispersion mode-locked ytterbium-doped fiber laser is used. A semiconductor saturable absorber mirror (SESAM) is used as a saturable absorber in the laser cavity. With the pump power of 865 mW, stable pulse train which is highly chirped with average repetition rate of 18.5 MHz and pulse width of 21 ps is obtained. The average output power is 8 mW, so the single pulse energy is 0.43 nJ. The full width at half maximum (FWHM) of output pulse is 4.32 nm. The spectrum has a steep edge.