The composite electromagnetic (EM) scattering characteristics of low-altitude target above valley composite rough surface are studied. The composite rough surface modeling theory is adopted to simulate the natural cavity structure of valley environment. Aiming at efficiently and accurately calculate the composite EM scattering from low-altitude target above valley environment, a hybrid method combining shooting and bouncing ray (SBR) technique and equivalent edge currents (EEC) method is proposed, in which SBR method based on the ray-density normalization (RDN) is applied to consider the multiple interactions between target and environment, and EEC method meliorates target's edge diffraction. Numerical examples illustrate the efficiency and validation of proposed hybrid method. Finally, based on the hybrid SBR-EEC method, the EM scattering characteristics of low-altitude target above valley environment are further investigated to show scattering mechanisms of this composite model and provide some useful conclusions through physical phenomena.INDEX TERMS Valley composite rough surface, shooting and bouncing ray technique, equivalent edge currents method, composite electromagnetic scattering.