Abstract: Thermoplastic polyester elastomer (TPEE) is extremely flammable, which seriously hinders its application in the fields of electronics and electrical, wire sheath, charging station, etc. TPEE composites with high flame retardancy were prepared by adding aluminum diethylphosphinate (AlPi) and melamine polyphosphate (MPP) flame retardant into TPEE matrix through internal mixing and hot pressing process. The flame retardancy of the TPEE composites was studied by limiting oxygen index (LOI), vertical burning (UL-94) and cone calorimeter (CONE) tests. The results show that AlPi combined with MPP can achieve high-efficiency flame retardancy of TPEE composites. In addition, the TPEE composite with 22wt%AlPi and MPP passed the UL-94 V-0 rating and its LOI value increase from 19.3% to 31.5%, accompanied with 27.6% reduction in the total heat release and 64.8% reduction of the peak heat release rate compared to pure TPEE. The thermal stabilities, mechanical properties, and electrical properties of the TPEE composites, as well as the microscopic morphology of the composites before and after ablation were studied by thermogravimetric analyzer (TGA), SEM, universal testing machine and electrical insulation test. The results indicate that the flame retardant mechanism of the composite flame retardant system is the barrier action of intumescent char layer in the condense phase. The composite flame retardant system can promote the decomposition of TPEE into carbon. The mechanical properties, electrical insulation properties and microtopography tests show that the combination of AlPi and MPP can improve the electrical insulation performance, but reduce the mechanical properties of TPEE composites due to their poor compatibility with TPEE matrix.