To enhance the flame retardancy of cable materials, a low density polyethylene/thermoplastic elastomer matrix (LDPE/TPE) was prepared, and flame-retardant materials such as modified aluminum hydroxide (ATH), microencapsulated red phosphorus (MRP), alumina (Al₂O₃), and organically modified silica (SiO₂) were added to improve the properties of the composites under electron beam radiation crosslinking. The results show that with the increase of TPE component, the melt flow rate (MFR) of the blend initially increases and then decreases. When the TPE content is 28%, the MFR of the blend reaches its maximum at 5.93 g/10 min. A small additive amount of TPE can enhance the processing properties of the LDPE/TPE blend. When flame retardant materials are compounded and filled, with the addition of 50 parts ATH, 30 parts MRP, 30 parts Al₂O₃, and 10 parts organically modified SiO₂, the comprehensive property of the composite is optimal. As the radiation dose increase, the gel content of the composite initially increases and then stabilizes.