With a new round of hydropower development in China, a large number of water conservancy and hydropower projects have been started, and many of them are rockfill dam. Rockfill dam and cofferdam used granular rockfill roller compaction construction, which has low cost, convenient construction, however, with the dam height increase, dam body (cofferdam) section will constantly increase, not only human, material and financial will be spent large, but also construction time will be extend, because of small friction angle and lower or none cohesion of rockfill. If we can improve the cohesion and friction angle of the rockfill, it will greatly reduce the dam section size and project cost. Although the roller compaction construction has the characteristics of convenient construction and high material strength, but as a kind of concrete materials with low water cement ratio, the colloid material proportion is still relatively large, high cost. Obviously, added only trace amounts of colloidal material without the change of construction process, that can improve the mechanical indexes of rockfill is the ideal choice. However, there is a lack of research results in effects of the rockfill filling trace amounts of colloidal material. In this paper, Study on the mechanical properties of the rockfill filling trace amounts of colloidal material has been done through large-scale triaxial shear test, to obtained forced deformation laws and constitutive model of the new material.