Under static compression molding (CM) of ultra-high molecular weight polyethylene (UHMWPE), 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, this study employed density measurements, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscopy (AFM), tensile testing, and wear resistance evaluation to investigate the promoting effect of pulse vibration pressure during the densification stage of pulse vibration molding (PVM) on UHMWPE particle interfacial fusion and its mechanisms governing microstructure and mechanical properties. The results demonstrate that the pulse vibration force during densification enforced mechanical interlocking among UHMWPE particles while simultaneously generating inter-particle frictional heat and internal plastic dissipation heat, thereby weakening particle rigidity and effectively eliminating voids between nascent particles and secondary aggregates, thus resolving the gas-entrapment issue inherent to CM. Microstructural analysis revealed that as the pulse vibration frequency increased to 5 Hz, the PVM sample molded at 170 °C (PVM-5Hz) achieved thorough densification, which facilitated molecular chain diffusion and penetration across the interfaces of both primary particles and secondary aggregates during melt hot-pressing. Compared with CM samples molded at 210 °C, PVM-5Hz exhibited a fracture strength increase of over 15%, a wear rate reduction of approximately 30%, and superior overall mechanical performance. The strengthening mechanism was 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.