The catalytic behavior of the novel tin(II) n-butyl L-lactate (Sn(OCH(CH3)COOnC(4)H(9))(2)) initiator in the ring opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) was firstly investigated by non-isothermal DSC. The Sn (OCH(CH3)COOnC(4)H(9))(2) initiator was successfully synthesized from the reaction of tin(II) chloride (SnCl2), diethylamine (Et2NH) and n-butyl L-lactate (CH3CH(OH)COOnC(4)H(9)). The synthesized Sn(OCH (CH3)COOnC(4)H(9))(2) was characterized by FT-IR, H-1 NMR and C-13 NMR techniques. The advantages of this initiator were high oxygen-moisture stability and solubility in common organic solvent. From DSC analysis, the polymerization rate of epsilon-CL was controlled by Sn(OCH(CH3)COOnC(4)H(9))(2) concentration. The average values of activation energy (Ea) obtained from Starink isoconversional method for the ROP of epsilon-CL initiated by 1.0, 2.0 and 3.0 mol% of Sn(OCH(CH3)COOnC(4)H(9))(2) were 74 +/- 5, 72 +/- 5 and 68 +/- 2 kJ/mol, respectively. Furthermore, the aggregation and non-aggregation equilibrium of Sn(OCH(CH3)COOnC(4)H(9))(2) initiator in the ROP of epsilon-CL was also investigated by non-isothermal DSC. The degree of aggregation (m) of initiator was rapidly determined using new derived equation based on non-isothermal DSC approach. The polymerization mechanism was also studied and proposed through the coordination-insertion mechanism.