A New random linear copolyester Poly(1,4-dithiane 2,5-diol succinate-co-1,10 decane diol succinate), PDDS was synthesized by direct melt polycondensation method using 1,4-dithiane 2,5-diol and 1,10 decane diol and Succinic acid with Titanium tetra isopropoxide as catalyst. As the polymers with sulphur atom in the main chain has excellent properties and wider applications especially in making lens, it led us to synthesis a copolyester with sulphur moiety in main chain and study its biomedical property. A thorough literature survey revealed that 1,4-dithiane 2,5-diol is used as a monomer in the synthesis of polyurethane sealing compound and used as an biocontrol agent, crosslinking agent and chain extenders in polymerisation technique. The Synthesised copolyester PDDS was characterized by determining its inherent viscosity, Solubility, Glass transistion temperature (DSC), crystalline nature (XRD), FTIR, 1H-NMR and 13C-NMR spectroscopy. The biomedical properties such as antioxidant, antimicrobial and in vitro cytotoxicity against normal (Vero cell line) and cancer (A549 lung cancer cell line) by MTT Assay of synthesized copolyester PDDS were also studied.