<p>Without weakening the comprehensive properties of the epoxy resin (EP) substrate itself, adding functional materials to increase the burning difficulty of EP and reduce the release of toxic and harmful smoke is a great challenge. In this work, Co-Ca-Fe layered double hydroxide hybrid flame retardant (DOPO-LDHS) with surface/interlayer Functionalization of 9, 10-dihydro-9-oxa-10-phosphate-10-oxide (DOPO) and phenylphosphonic acid (PPO) were synthesized. The 10 wt% DOPO-LDHs modified EP exhibited superior flame retardancy in both gas and condensed phases. The peak Heat release rate, total smoke production, CO production, and smoke production rate of EP composites containing 10 wt% DOPO-LDHs were reduced by 31.2%, 31.7%, 37% and 35%, respectively. DOPO-LDHs contribute to the formation of the condensed phase with a dense carbon layer that is resistant to thermal oxidation, and the synergistic action of DOPO and OPA releases non-flammable phosphorus-containing radicals in the gas phase. Meanwhile, the oxides formed by the physical phase transformation of LDHs catalyze the transformation of CO to form CO₂ to reduce the release of harmful gases. In addition, the EP/DOPO-LDHs composites have good mechanical properties, and no obvious weakening for tensile and flexural strengths had occurred. This work provided a new idea for the green flame retardant system with layered double hydroxides as functional carriers.</p> Graphical Abstract <p></p>