In the reaction of Mg(3s3p(1)P(1)) with H-2, we have constructed a new version of ab initio potential energy surfaces (PESs) for 2A' and 1A' states and their corresponding fit energy functions, on which 50 000 trajectory calculations are performed. The improvement of the current quasiclassical trajectory (QCT) calculations has made dynamical parameters more reliable than those reported previously. For instance, the obtained bimodal rotational distribution of MgH (v = 0), with a peak ratio of ca. 2:1 for the high-N to low-N components, is consistent with the experimental findings. The evaluated vibrational population ratio of ca. 0.52 for v = 1 to v = 0 is also within the range of observation, 0.7 +/- 0.2. In addition, this work provides new information about the formation of MgH rotational levels via the angular momentum analysis. The trajectory calculations reveals the relation of the rotational distribution to the impact parameter, b, and the relative angle, epsilon, between the orbital and rotational angular momenta of the products. The MgH is preferentially populated in the high-Ar levels at small b but favors the low-N distribution at acute-angle (<90) epsilon. The analysis of vector correlation provides insight into the behavior of the MgH rotational population.