Cohesive element is an important means to investigate the "dewetting" damage of propellant. The high filling ratio geometric model of propellant was constructed by the molecular dynamics method, and the mesoscopic finite element analysis model of propellant was constructed by combining the periodic geometry and periodic boundary treatment methods. The "dewetting" behavior of the interface between the particle and the matrix was simulated by using the cohesion element and PPR cohesive zone model. The mechanical response of propellant mesoscopic structure was analyzed under the uniaxial tensile and pure shear tests, and the damage mechanism of "dewetting" of propellant was studied. According to different volume fraction ratio, strain rate and cohesive strength, the influence law of "dewetting" damage was analyzed. The research methods and conclusions can provide a useful reference for the formulation of a new generation of high-performance propellant.