Intense electromagnetic pulse has posed a direct threat to dense electronic platforms such as aircraft. Antenna structure is an important coupling channel for intense electromagnetic pulse (EMP) entering the aircraft platform to produce electromagnetic environmental effects. It is of great significance to analyze the electromagnetic coupling response of platform airborne antenna through numerical simulation. The platform-antenna integrated coupling simulation is a typical method to solve multi-scale time-domain electromagnetic calculation problem. The tens meter platform contains hundreds of micro meter microstrip lines, circuit elements and other local fine structures. When the traditional FDTD method is used to simulate this kind of problems, the computational efficiency is very low due to the need of grid division. This paper introduces a time-domain hybrid method, which combines the non-uniform FDTD method with the thin wire FDTD method and the multi grid lumped element FDTD method, thus can effectively reduce the computational overheads. Combined with parallel computing technology, the transient voltage and current response of the antenna port can be calculated quickly. The method is successfully applied to the numerical simulation of UAV platform antenna integrated coupling.