Ring-opening polymerization of (D,L)-lactide ((D,L)-LA) initiated by single component rare earth tris(4-tert-butylphenolate)s has been carried out for the first time. The influences of rare earth element, solvent, temperature, monomer and initiator concentration as well as reaction time on the polymerization were investigated in detail. The kinetics study indicates that the polymerization rate is first order with respect to monomer concentration and initiator concentration, respectively. The overall activation energy of the ring-opening polymerization is 81.7 kJ.mol(-1). The intensity distribution of the various stereosequence resonances in the NMR spectra reveals that transesterification proceeds slowly during the polymerization at the temperatures less than or equal to 90degreesC. DSC data confirm the random distribution of the polymer. Mechanism studies showed that the (D,L)-lactide monomer inserted into the growing chains with the acyl-oxygen bond cleavage.