The Tm3+/Yb3+ codoped bismuth germanate glass substrates containing metal Ag nanoparticles (NPs) were synthesized by the conventional melting-quenching technique. The absorption band related to the surface plasmon resonance (SPR) of the silver NPs is located from 556 to 581 nm. Transmission electron microscopic image clearly reveals homogeneously dispersed Ag NPs with the size from 5 to 25 nm. The upconversion luminescence spectra in the range of 400~900 nm are measured. The upconversion mechanism of Tm3+/Yb3+ codoped bismuth germanate glass is also discussed. Upconversion luminescence exhibits three main emission bands of Tm3+ ions centered at 476 nm (blue), 649 nm (red) and 801 nm (near-infrared) due to 1G4→3H6, 1G4→3F4, 3H4→3H6 transitions, respectively. With the addition of the AgCl up to mass fraction of 0.2%, the intensities of these emission bands increase by 18.1, 8.3 and 6.4 folds, respectively. The enhancement of upconversion emission is attributed to the enhanced local field induced by Ag0 SPR and energy transfer from Ag0 to Tm3+ ions.