A series of biodegradable poly(ester-co-carbonate) multiblock copolymers consisting of poly(butylene succinate) and poly(butylene carbonate) (PBS-b-PBC) were synthesized successfully by chain-extension reaction of dihydroxyl terminated PBS-diol prepolymer and dihydroxyl terminated PBC-diol prepolymer using hexamethylene diisocyanate (HDI) as a chain extender. The chemical structures and molecular weights of copolymers were characterized by proton nuclear magnetic resonance (H-1 NMR) and gel permeation chromatography (GPC). The thermal properties, crystallization behavior, morphology and mechanical properties of PBS-b-PBC were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), phase-contrast optical microscopy (PCOM), and mechanical testing. It was found that the PBC soft segment is effective in enhancing the impact strength, while hardly decreases the melting point (T-m) of the copolymers. The resulting novel copolymers are expected to find a potential application in the area of biodegradable polymer materials.