Abstract: The study of composite electromagnetic scattering from target and rough surface is an important topic in computing electromagnetic fields. This study plays a significant role in target-detection (flying missiles and aircraft above ground or sea surface with low altitude; a ship on sea surface; tank targets above ground, etc.), resource exploration (exploration of minerals under the ground), which makes the research of composite electromagnetic scattering urgent and practical. When incident wave reach a target located on a rough sea/ground background, the electromagnetic wave will interact with the background, which affects the radar echo and the scattering properties of the target. Therefore, the existence of rough surface will increase the difficulty of target detection and recognition.