With the rapid development of high voltage switch and military industry, higher requirements are put forward for the arc erosion resistance of CuW composites. The density is a key factor affecting the arc erosion resistance of CuW composites. To further improve the density of CuW composites, double-particle-size hybrid CuW composites were designed based on the binary packing theory. Single-particle size CuW75 composites and double-particle size hybrid CuW composites were prepared by rapid hot-pressing sintering and infiltration process. The microstructure of CuW75 composites was characterized by JSM-IT100 tungsten filament scanning electron microscopy. The density of CuW75 composites was tested by New Classic MF density meter. The hardness of CuW75 composites was tested by 320HBS-3000 digital display Brinell hardness tester (loading 250 kg, loading time 30 s). The electrical conductivity of CuW75 composites was tested by Signma2008B1 digital conductivity meter. The intrinsic relationship between the density and microstructure of both single-particle CuW75 composites and double-particle size hybrid CuW composites were studied, and the arc erosion resistance of double-particle-size hybrid CuW composites was carried out on the JF04C electrical contact test system. The results showed that the microstructure of the double-particle size hybrid CuW composites was uniform, which effectively reduced the aggregation of W phase and Cu phase and improved the network connectivity of W phase and Cu phase. The density was 99.79%, which was 3.4% and 1.19% higher than that of CuW75 composites with single-particle size of 1 μm and 20 μm. It was 2.9% higher than the national standard of CuW75 composites, and the hardness was 6.7% higher than the national standard of CuW75 composites. The electrical contact process was divided into two steps:closure and disconnection. When the cathode and anode changed from the closed state to the disconnected state, the contact area of the cathode and anode became smaller, the resistance increased, and the formed Joule heat caused the temperature to rise rapidly. The high temperature generated by the arc would cause metal evaporation and liquid metal splashing on the material surface. Due to the uneven contact surface, the contact point was gradually reduced to one or several, and a melting bridge was formed between the melted metal, which increased the duration of the arc. After the anode and cathode were disconnected, the melting bridge gradually broke, so that the anode appeared a molten pool, and the cathode formed some conical bulge. The results of electrical contact experiment showed that hybrid CuW75 composites with double particle size had smaller fluctuations of welding force, and the average welding force was 11% lower than that of single-particle size CuW75 composites (1 μm). The average arc energy and average arc time decreased by 38% and 36%, respectively, compared with single-particle size CuW75 composites (1 μm). Moreover, the arc erosion area of double-particle size hybrid CuW composites were smaller and the erosion pit was shallower. The preparation of CuW composites with double-sized hybrid W particles can significantly improve the density and microstructure connectivity of the materials. The double-particle-size hybrid CuW composites can better disperse the arc with excellent welding resistance and arc erosion resistance.