A novel type of biodegradable non-phosphor detergent builder was prepared by anionic ring-opening copolymerization of disodium cis-epoxysuccinate and 2,3-oxiranernethane sulfonic acid sodium. The structure of the copolymer was confirmed by FTIR, (HNMR)-H-1 and X-ray diffraction. The molecular weights of the copolymers were 1,000-2,000 obtained from laser light scattering data indicating that they were oligomers. The builder performances and biodegradability of the copolymers were systematically investigated. The results demonstrate that the copolymer is amorphous, and it exhibits high calcium-ion chelating ability and dispersion capacity and buffer capacity which are even better than that of sodium tripolyphosphate and sodium polyacrylate. Moreover, this copolymeric detergent builder displays excellent biodegradability, which can meet the requirement of environment-friendly and non-polluting. These copolymers of disodium cis-epoxysuccinate and 2,3-oxiranernethane sulfonic acid sodium have great potential in theory and application as effective and environmentally friendly detergent builders.