Quasi-classical trajectory (QCT) calculations have been performed to study the product polarization behaviours in the reaction O( 3 P) + D 2 (v = 0, j = 0) → OD + D. By running trajectories on the 3 A and 3 A potential energy surfaces (PESs), vector correlations such as the distributions of the polarization-dependent differential cross sections (PDDCSs), the angular distributions of P (θr) and P (φr) are presented. Isotope effect is discussed in this work by a comprehensive comparison with the reaction O( 3 P) + H 2 (v = 0, j = 0) → H + H. Common characteristics as well as differences are discussed in product alignment and orientation for the two reactions. The isotope mass effect differs on the two potential energy surfaces: the isotope mass effect has stronger influence on P (θr) and PDDCSs of the 3 A PES while the opposite on P (φr) of the 3 A potential energy surface.