In this work, the ROPs of L-lactide were performed in a TSMR and a TSE, respectively. The TSMR (see Fig. 1) was a loop reactor consisting of a gear pump and four identical corrugated plate-type static mixers. The typical procedure for ROP of L-lactide in the TSMR was as follows. Equimolar stannous octoate(Sn(Oct)2) and triphenylphosphine(PPh3) (complex catalysts system) were added into the melted L-lactide monomer, which was previously mixed with 0.5 wt% antioxidant 24. The melted mixture was then fed into the pre-vacuumed TSMR. The ROP of L-lactide occurred when the reactants flew circularly and were mixed in the loop reactor. The resultant polymers were collected at the discharge gate and rapidly cooled down to room temperature. Then they were dissolved in dichloromethane and precipitated with ethyl alcohol. The information about ROP of L-lactide in the TSE was reported in our previous work [9]. The screw of the extruder was equipped with normal screw elements and kneading blocks, which resulted in different shear rates of reactants. The number-average molecular weight (Mn), weight-average mo- lecular weight (Mw) and PDI of the resultant polymers were deter- mined by GPC. The viscosity-average molecular weight (Mv) of the products was determined according to the reported method [10]. Optical purity(OP) of the resultant polymers was determined by the reported method [11].