Diels-Alder (DA) reaction has long been used to construct ring systems in organic synthesis, while site-and regioselectivity of this important reaction remain unsolved. Unlike those reactions which undergo an ionic mechanism, it is not easy to merely extract the reaction core atoms and calculate their QM properties for prediction. In a previous work, Grzybowski et al. divided the reaction cores of DA reaction into 10 substituents and used Hammett and TSEI descriptors of 10 substituents as the input of RF model. Here, we focused on the 10 atoms that are connected to the core (the highlighted atoms in Figure ) rather than the substituents, then calculated the qmdesc descriptors for them while the TSEI descriptors remained unchanged. Considering the symmetry in the DA reaction, each entry in the dataset was augmented to four with half of them labelled as 1 (the experimental product) and the rest labelled as 0.