Scanning tunneling microscopy (STM) can achieve atomic-level resolution (its longitudinal and transverse resolutions are 0.01 and 0.1 nm, respectively), thus could realize real-time in-situ observation of the dynamic process of the surface and interface, such as molecular adsorption and desorption behavior, surface reaction, molecular diffusion and so on. Therefore, the in situ study of electrochemical reactions and electrical properties at the molecular level can be realized based on the high spatial resolution of STM. The two-dimensional covalent organic frameworks (COF) thin films with single molecular layer and nanometer thickness, prepared by surface and interfacial molecular reaction strategy, are expected to become electrochemical and electronic materials with superior performance, due to their superior stability and potential excellent electronic conductivity, and are suitable for device construction. The main content of this research is to study the electrical reactions, electrical properties and catalytic properties of single molecule and single molecule layers by STM and AFM, and to prepare functional organic thin films of single molecule layer and few layers by surface interfacial molecular reactions, so as to realize electrochemical and electronic applications and device construction.