Abstract: Three polyurea greases with the same mass fraction of thickener were prepared by the same method using three kinds of monoamines with typical molecular structure. The microstructure of thickeners in three polyurea greases was characterized by scanning electron microscopy. The results showed that the microstructure of thickener in octadecylamine polyurea grease was entangled fiber structure, and which in cyclohexylamine and aniline polyurea grease was stack spindle. Moreover, the thixotropic properties, storage modulus, loss modulus, and apparent viscosity of three polyurea greases were investigated at different temperatures. The relationship between rheological properties of polyurea greases and the micromorphology and intermolecular forces of the thickener was explained. This study provided a good theoretical guidance for the design and development of polyurea greases, and promote the research and application of polyurea greases.