Abstract: Borosilicate matrices are widely accepted as containment of high level wastes on account of its good chemical durability and endurable formation temperatures. However, the yellow second phase (yellow phase) will be produced during melting if the high level liquid wastes contain high concentration sulfate, which harms the performances of vitrification form. To resolve the yellow phase problems, it is necessary to understand sulphur behaviors in the borosilicate waste glasses, especially the relation between sulfate solubility and glass composition. A large amount of experiments have been done to explore the relation. The experiment results show that the relation between the glass composition parameter x(O^-) and sulfate solubility is linear and the relation between the glass composition parameter x²(O^-)/x(O⁰) and sulfate solubility is logarithmic.