A novel Er3+/Yb3+ codoped phosphate glass WM4 was designed and developed, which exhibited good chemical durability in molten salts and good spectroscopic properties. The stimulated emission cross-section of 4I13/2→4I15/2 transition of Er3+ ions and Judd-Ofelt intensity parameters Ωt (t=2,4,6) were obtained by analyzing the room temperature absorption spectrum; the stimulated emission cross-section of 4I13/2→4I15/2 transition of Er3+ ions was 0.72×10-20 cm2, which is larger than that of Schott′s IOG1, 0.67×10-20 cm2. Preliminary results of ion exchange at different time and temperature with varying molten salt compositions indicated that WM4 glass was suitable for ion exchange process and Er3+-doped waveguide amplifier (EDWA) application, and single mode optical waveguide at 1.55 μm was fabricated. The propagation loss of all the waveguides was less than 1 dB/cm.