Erbium-doped bismuth-based glasses with compositions of 43Bi2O3-xB2O3-(57-x) SiO2 (x=10, 20, 30, 40, 50 mol%) were prepared, the absorption spectrum, emission spectrum, fluorescence lifetime and fluorescence intensity were measured, and the compositional dependence of spectroscopic properties of Er3+ ions have been investigated according to the Judd-Ofelt theory and McCumber theory. With the increasing of B2O3 content in the glass composition, the Judd-Ofelt parameter Ω6, full width at half maximum (FWHM) of fluorescence and calculated spontaneous emission probability of the 4I15/2->I13/2 increase, while the fluorescence lifetime, fluorescence emission intensity and simulated emission peak cross-section decrease, and the bandwidth quality factor σepeak × FWHM reaches maximum at the B2O3 content of 30 mol%. Compared-with other oxide and fluoride glasses ever reported, the erbium-doped bismuth-based glass shows favorable optical properties and can be used as an excellent gain media for broadband amplifiers. Also, the above results will provide theoretical significance for the determining superior glass composition content of new type broadband bismuth-based erbium-doped fiber.