Abstract: Understanding the origin of friction and the evolution of energy is the theoretical foundation for actively controlling interfacial frictional behavior. The classical Prandtl-Tomlinson （P-T） model, as a typical model describing stick–slip motion in atomic-scale friction, reveals the essence of mechanical instability through simplified parameters and establishes a connection between macroscopic friction behavior and atomic-scale potential energy surfaces. However, systematic analyses of the energy evolution pathways and the effects of key parameters in this model remain insufficient. To address this gap, a quasistatic analysis of the motion mechanism in nanoscale friction is conducted based on the P–T model. The generation of stick–slip motion and its frictional characteristics are analyzed, and the nonequilibrium energy evolution process influenced by relevant factors is demonstrated. Furthermore, the independent regulatory roles and synergistic effects of the potential barrier height and the elastic constant are quantitatively clarified: the potential barrier height determines the upper limit of dissipation and the maximum static friction, while the elastic constant governs the maximum elastic potential energy and the energy dissipated per slip event. By varying both parameters together, the dimensionless competitive ratio of the interfacial periodic potential to the elastic constant is quantitatively interpreted: this ratio not only determines the critical threshold for the stick–slip to smooth-sliding transition but also scales the intensity of energy dissipation. By linking the simplified potential energy surface model to macroscopic friction behavior, this study deepens the understanding of the physical mechanisms of nanoscale friction and aims to provide a theoretical basis for reducing friction through the modulation of interfacial properties and mechanical performance.