Abstract: Bismaleimide-triazine resin (BT resin) and its modified variants are widely used in the copper clad laminate (CCL) industry due to their excellent thermomechanical properties. However, BT resin exhibits high dielectric constant, poor toughness, and suboptimal flame-retardant performance. In this study, a BCD ternary resin system-based CCL was developed using phosphorus-containing bismaleimide (DOPO-BMI) and dicyclopentadiene cyanate ester (DCPD-CE) as the BT resin matrix. The mass ratio of DOPO-BMI to DCPD-CE was adjusted, and 2,2'-diallyl bisphenol A (DBA) was introduced as a modifier, and the properties of the resin and the resulting CCLs were systematically investigated. Results show that DBA reduces the curing temperature of the resin system and forms a structurally uniform interpenetrating network. The BCD ternary resin system-based CCL exhibits outstanding thermodynamic performance, with a 5% weight loss temperature exceeding 400℃, a glass transition temperature (T_g) ranging from 180℃ to 242℃, and a Z-axis coefficient of thermal expansion (Z-CTE) as low as 10.24–23.58 ppm/℃. The introduction of DBA can decrease the dielectric constant and dielectric loss of the system while enhancing the peel strength between the resin and copper foil. Additionally, the flame retardancy of the CCL meets the UL 94 V-0 standard.