Diamond-based composites have wide applications in tooling areas due to super-high hardness and wear-resistance. Sintering of diamond with other metallic phases is of a great challenge, because diamond is active with most metals and the bonding of diamond-diamond occurs only under extreme conditions. High entropy alloys (HEAs) have great potential in acting as binder phases with diamond, since they have high flexibility in the adjustments of microstructures and mechanical properties. Therefore, we introduced our recent work on developing diamond-based composites with high entropy alloy binders, including CuCoCrNi and CoNiFe alloys. Spark plasma sintering and high temperature high pressure sintering (~6GPa) were conducted as densification methods. High throughput materials design was also studied, and new compositions of HEAs with proper mechanical properties were proposed. Results indicated that HEAs have good compatibility with diamond in considering the interfacial bonding strength, and under high temperature and high pressure, CuNiFe alloy can introduce more sp3 bonding in between diamond particles than Co. Therefore, diamond-based composites with HEAs binder have higher transverse fracture strength and better wear resistance than conventional diamond composites. The microstructures and strengthening mechanisms of above two diamond composites were analyzed in detail.