Cement-based materials are brittle and easy to crack, which are concerned as the key problems to be solved in engineering application. The microscale brittleness of the material phases of cement-based materials needs to be investigated, and a relationship between the micro-scale brittleness and the overall brittleness needs to be established for the toughening design of cement-based materials. In this work, the fracture toughness-displacement curves were obtained via micro-scratch test, and the phases corresponding to the scratch area were analyzed by high resolution scanning electron microscopy, thus charactering quantitatively the fracture toughness of cement paste and its material phases, and establishing the relationship between the overall brittleness of cement paste and the brittleness of calcium silicate hydrate gel.