A novel cyclic carbonate monomer 5-methyl-5-(succinimide-N-oxycarbonyl)-1,3-dioxan-2-one (MSTC) was prepared. The copolymers of MSTC with caprolactone (CL) were further synthesized by ring-opening copolymerization. The copolymer with amido-amine pendent groups were obtained by aminolysis of poly(MSTC-co-CL) with ethylenediamine. These copolymers were characterized by IR, H-1 NMR, C-13 NMR spectroscopies and GPC. The hydrophilicity and degradability of the copolymers with amidoamine pendent groups were greatly improved in comparison with the PCL homopolymer.