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Glass with 5Ta2O5, xBi2O3, (95–x)P2O5 for 10≤ x ≤ 20 mol % formula was obtained by the normal melt-quench technique and identified by DRX, DSC analysis, Infrared spectroscopy, and followed by the study of the dielectric and optical properties. Glass transition temperature (Tg) is found to grow linearlywith bismuth oxide concentration and goes from 524°C for x=10 to 582°C for x=20 mol %. The density ρ increases with increasing Bi2O3 content and molar volume (VM) diminish when Bi2O3 content rises. The IR study shows the presence of BiO6 and PO3 structural groups and reveals depolymerization of the phosphate links by the creation of the Bi–O–P groups which are due to the incorporation of Bi–O bonds. The partial replacement of P2O5 by Bi2O3 shows that the variation of ɛr' and tan δ depend on Bi2O3 contents. By UV absorption, optical properties of glasses were found in the wavelength limit from 250 to 800nm. The energy band gap was calculated using the optical absorption spectrum and was interpreted as a reflection of the structural changes that take place in the glasses as the Bi2O3 content increases.