Edge-cladding is a key factor in improving saturated small signal gain coefficient 'beta's of large laser disc glass. In this paper, the glasses were melted with traditional method. The influences of mixed alkali effect (MAE) on refractive index, thermal expansion coefficient 'alpha', glass transition temperature Tg, dilatometer softening temperature Td, and relative chemical durability of phosphate edge-cladding glasses were studied. The results reveal that when Li/(Na+Li)=0.5, Tg, Td, and dissolution rate (DR) reach a minimal value. These results are preferred in phosphate edge-cladding glasses.