Influences of arm number and arm length of poly(D,L-lactide)s (PDLLs) on their thermal properties were investigated. The PDLLs with linear (1 arm) and star (4, 6 and 16 arms) shapes were synthesized via ring-opening polymerization of DLL monomer in bulk at 130°C for 24 h under nitrogen atmosphere. Stannous octoate was used as a catalyst. Initiators containing hydroxyl end groups of 1, 4, 6 and 16 were chosen as core molecules for synthesizing 1, 4, 6 and 16armed PDLLs, respectively. Thermal properties of the PDLLs observed from their differential scanning calorimetric and thermogravimetric thermograms strongly depended upon their arm numbers and arm lengths. For the same DLL/initiator ratio (208/1 by mole), glass transition temperatures (T_g) and temperatures of maximum decomposition rate (T_d,max) of the PDLLs decreased when the arm length decreased (or arm number increased). For similar PDLL arm lengths (4,500 and 4,900 g moL^-1 for 6-armed star-shaped and 1 -armed linear PDLLs, respectively), the T_g and T_d,max of star-shaped PDLL was higher than that of the linear PDLL.