Unlike conventional oxide ferroelectrics with rigid lattices, van der Waals (vdW) ferroelectrics feature covalently bonded monolayers interconnected by vdW interactions across the interlayer. The structural discontinuity introduced by vdW interlayer distance may lead to the anisotropic switching dynamics along in plane and out of plane, directly impacting the performance of ferroelectric devices. However, the anisotropic switching mechanisms of the domain walls (DWs) in vdW ferroelectrics remain unclear, constrained by the spatial-temporal resolution limitations in both theoretical simulations and experimental observations. Here, we employ the machine-learning potential molecular dynamics to investigate the atomic structure and the dynamics of DWs in multilayer $2H$ α-$\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3$. Our results reveal that the in-plane DWs of $2H$ α-$\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3$ contain a nonpolarized layer sandwiched between two oppositely polarized layers, which avoids an abrupt polarization reversal with high electrostatic energy. Such nonpolarized layer enables layer-by-layer domain switching dynamics in a multilayer structure under external field. We further reveal that two types of out-of-plane DWs exhibit distinct switching behaviors due to the difference in DW motion energy barriers. Notably, the motion of out-of-plane DWs precedes that of the in-plane DWs under an external electric field. These findings reveal the anisotropic switching dynamics in multilayer $2H$ α-$\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3$ and provide critical insight for designing vdW ferroelectric devices based on DW engineering.

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• Ferroelectricity
• van der Waals systems
• Molecular dynamics