Biodegradable aliphatic poly(butylene succinate-co-diethylene succinate)(PBDGS) were synthesized from succinate acid and 1,4-butanediol/diethylene glycol through direct polymerization. The products were characterized with 1H-NMR, GPC and DSC, etc. The influence of monomer ratio on thermal properties, mechanical properties, degradability and hydrophilicity of the copolymers were studied. The results showed that the introduction of DEG can suppress the chain crystallizability and improve hydrophilicity of PBDGS. The degradation of copolymers is obviously higher than that of neat PBS.