The highly isoselective ring-opening polymerization (ROP) of racemic lactide is regarded as a valuable strategy for the synthesis of stereocomplex polylactide. In the present contribution, we report the novel yttrium bis(phenolate) ether complexes for catalyzing ROP of raceniic lactide in high activity (TOP) aria,excellent isotactic selectivity (P-1) (P-i = 0.90, TOP = 120 h(-1) at -15 degrees C; P = 0.84, TOF = 2280 h(-1) at 25 degrees C). Kinetic and computational studies provide a fundamental understanding of the steteocontrol mechanism governing polymerization reactions mediated by yttrium catalysts.