The trends of present design in electronic systems are towards high speed, small size, and lower voltage levels. Due to these trends, the influence of ESD becomes a more serious problem for an EMC designer. How to precisely evaluate the effect of ESD by measurement and simulation, and try to solve these questions quickly is the most important topic at present. In this thesis we introduce several measurement approaches to ESD. We try to find the equivalent circuit model of the ESD gun operated in our lab, and construct the simulation model by Agilent ADS software. Good agreement between simulation and measurement demonstrates the correctness of the model for this ESD gun. By combining the simulation model of ESD gun with equivalent circuit of DUT extracted by Ansoft Q3D software, it is found this method can evaluate the ESD phenomena of DUT fast and precisely. In addition, with this method some phenomena restricted by measurement can be studied. Finally two real products including a PDA (floating system) and the mainboard in the desktop computer system (grounding system) are discussed in detail.