Under the static compression molding (CM) of ultra-high molecular weight polyethylene (UHMWPE), the insufficient densification tends to cause gas entrapment in the melt, leading to defects that severely compromise the mechanical performance of the final products. Using CM samples as a reference, in this study, density measurements, differential scanning calorimetry, scanning electron microscopy, atomic force microscopy, tensile testing, and wear resistance evaluation were employed to investigate the promoting effect of pulse vibration pressure during the densification stage of pulse vibration molding (PVM) on the interfacial fusion of UHMWPE particles and its mechanism governing microstructure and mechanical properties. The results demonstrate that the pulse vibration force during densification enforces the mechanical interlocking among UHMWPE particles while simultaneously generating inter-particle frictional heat and internal plastic dissipation heat, thereby weakening the rigidity of the particle and effectively eliminating the voids between the nascent particles and secondary aggregates, thus resolving the gas-entrapment issue inherent to CM. The microstructural analysis reveals that as the pulse vibration frequency increases to 5 Hz, the PVM sample molded at 170 °C (PVM-5 Hz) achieves thorough densification, which facilitates the diffusion and penetration of molecular chains across the interfaces of both primary particles and secondary aggregates during the melt hot-pressing stage. Compared with the CM samples molded at 210 °C, PVM-5 Hz exhibits a fracture strength increase of over 15%, a wear rate reduction of approximately 30%, and superior overall mechanical performance. The strengthening mechanism is primarily attributed to defect-free interfacial fusion induced by high-frequency pulse vibration force, coupled with the retention of a highly crystalline structural feature enabled by low-temperature processing.