High-performance epoxy resins (EPs) with ultimate flame retardancy, particularly in terms of smoke suppression (as asphyxiation is the primary cause of death in fires), remain a significant challenge. To address this issue, we propose a feasible multiple crosslinking strategy by incorporating an additive flame retardant (abbreviated as BPPDN) containing self-crosslinking groups to construct multi-crosslinking networks during the curing of EPs. Using this strategy, the BPPDN/EP flame-retardant samples achieved a V-0 rating in the UL-94 test in the absence of conventional flame-retardant elements such as halogens or phosphorus. Among the rest, 15BPPDN/EP had remarkable low fire hazards, with total smoke production and peak heat release rate reduced by 38.7 % and 22.2 %, respectively. Surprisingly, the 15BPPDN/EP material maintained its high transparency, excellent ultraviolet shielding, and dielectric properties (specifically, the dielectric constant decreased from 5.19 to 3.46; the dielectric loss decreased from 0.0066 to 0.0045), as well as its ultrahigh tensile strength (increased by 63 %), flexural strength (by 48 %) and impact strength (by 75 %). This paper investigates in detail the effects of BPPDN on the curing process, thermal properties, mechanical properties, dielectric properties, and flame retardancy of EPs, providing a new direction for the design of highly transparent, multifunctional high-performance flame-retardant thermosetting resins without the need for conventional flame-retardant elements.