A tunable fiber polarizer based on the selectively silver-coated large-core suspended-core fiber (LSCF) was proposed. A thin silver layer was coated on the inner surface of two opposite air holes of the LSCF by the chemical liquid-phase deposition method. The $y$-polarized light (parallel to the two silver-coated air holes) will excite surface plasmon resonance and experience large transmission loss, while the $x$-polarized light does not, resulting in a fiber polarizer. By varying the liquid filled in the microchannels of the LSCF, the operating wavelength can be tuned in the visible and near infrared region along with the surface plasmon resonance wavelength. The dependence of the polarization characteristics on the fiber length was experimentally investigated. The maximum polarization extinction ratio (PER) of 20.1 dB, 19.6 dB, and 18.3 dB and insertion loss (IL) of 2.24 dB, 2.56 dB, and 2.08 dB are achieved with the optimal fiber length of 16 cm at the operating wavelengths of 565.4 nm, 626.7 nm, and 739.7 nm, respectively. Compared with the multimode fiber-based polarizers reported previously, the proposed selectively silver-coated LSCF polarizer exhibits higher PER and lower IL.