A self-similar k-graph is a pair consisting of a discrete group and a k-graph, such that the group acts on the k-graph self-similarly. For such a pair, one can associate it a universal C*-algebra, called the self-similar k-graph C*-algebra. This class of C*-algebras embraces many important and interesting C*-algebras, such as the higher rank graph C*-algebras of Kumjian-Pask, the Katsura algebra, the Nekrashevych algebra, and the Exel-Pardo algebra. In this talk, I will present some results about those C*-algebras, which are based on joint work with Hui Li.