The visual analysis techniques of weak interactions in chemical systems represented by non-covalent interaction (NCI) method have become increasingly popular in the past 10 years. These methods allow chemists to conveniently and intuitively understand what kinds of interactions exist in which areas, and to a certain extent the interaction strengths can also be analyzed quantitatively. This chapter presents a comprehensive and systematic introduction to NCI and various subsequent analysis methods that closely related to it. Readers will learn about the idea, principle, characteristics, and application scope of different methods. At the same time, this chapter will briefly introduce the Multiwfn program that can realize these analyses.