This course describes and explains the properties of molecules from the perspective of electronic structure. The main contents include the theoretical basis of electronic structure, the basic techniques of electronic structure calculation and its applications in analyzing molecular properties, interpreting and predicting chemical reactions. This course will provide students in chemistry, molecular physics, chemistry, environment, energy, and materials research with an atomic-level perspective and practical computational and analytical techniques that will help overcome the shortcomings of microscopic observation in experimental science. On the basis of theoretical teaching, this course will demonstrate a lot of practical operation on the computer.