Mining graph data has become a popular research topic in computer science and has been widely studied in both academia and industry given the increasing amount of network data in the recent years. However, the huge amount of network data has posed great challenges for efficient analysis. This motivates the advent of graph representation which maps the graph into a low-dimension vector space, keeping original graph structure and supporting graph inference. The investigation on efficient representation of a graph has profound theoretical significance and important realistic meaning, we therefore introduce some basic ideas in graph representation/network embedding as well as some representative models in this chapter. them may have its own terminology, e.g., a vertice and an edge in a graph v.s. a node and a link in a network. Therefore we will exchangeably use graph representation and network embedding without further explanations in the remainder of this chapter. The core of mining graphs/networks relies heavily on properly representing graphs/networks, making representation learning on graphs/networks a fundamental research problem in both academia and industry. Traditional representation approaches represent graphs directly based on their topologies, resulting in many issues including sparseness, high computational complexities etc., which actuates the advent of machine learning based methods that explore the latent representations capable of capturing extra information in addition to topological structures for graphs in vector space. As such, the ability to find "good" latent representations for graphs plays an important role in accurate graph representations. However, learning network representations faces challenges as follows:1. High non-linearity. As is claimed by Luo et al. [43], the network has highly non-linear underlying structure. Accordingly, it is a rather challenging work to design a proper model to capture the highly non-linear structure.2. Structure-preserving. With the aim of supporting network analysis applications, preserving the network structure is required for network embedding. However, the underlying structure of the network is quite complex [55]. In that the similarity of vertexes depends on both the local and global network structure, it is a tough problem to preserve the local and global structure simultaneously.3. Property-preserving. Real-world networks are normally very complex, their formation and evolution are accompanied with various properties such as uncertainties and dynamics. Capturing these properties in graph representation is of significant importance and poses great challenges. 4. Sparsity. Real-world networks are often too sparse to provide adequate observed links for utilization, consequently causing unsatisfactory performances [50]. Many network embedding methods have been put forward, which adopt shallow models like IsoMAP [62], Laplacian Eigenmaps (LE) [4] and Line [61]. However, on account of the limited representation ability [6], it is challenging for them to captu...