This study explored the influence of low temperature glow discharged argon (Ar) plasma on interfacial performance and impact resistance of ultra-high molecular weight polyethylene (UHMWPE) inter-ply hybrid composites. The composites were composed of UHMWPE and meta-aramid plain woven laminates with shear thickening fluid (STF). Water contact angle and drop-weight resistance of the composites with various Ar plasma treatment parameters were tested to investigate the interfacial performance and impact properties of the composites. The tested treatment parameters of this study included treating time, treating power, and gas flow rate. It was found that the best interfacial adhesion of UHMWPE and the impact resistance of the composites was realized at the plasma treatment power of 100 W, treatment time of 150 s, and gas flow rate of 4 sccm. In the follow-up research, this study conducted ballistic test to further explore the bulletproof effect and application prospect of this material.