Very recently, our group proposed a new ∆-ML strategy using PIP-NN for the construction of the full-dimensional high-accuracy PES of complicated systems. Firstly, a suitable low-level method (often DFT) was selected after comprehensively testing and a low-level PES (VLL) is firstly fitted by the PIP-NN method based on ample DFT calculated points that cover all dynamically relevant regions. The next step is to select points from the existing DFT dataset to construct the correction PES (∆VHL-LL) between VLL and VHL. Then ∆VHL-LL is used to predict the energy differences of the remaining points whose energies are not computed directly at the target high-level method. Namely, the target high-level energy of these remaining points is the sum of the DFT energy and the predicted energy difference by ∆VHL-LL.