Boost converter occupies a very important position in the area of switching power supply, it is widely used in various power equipment for a long time, while the transient working process from start to steady-state are not involved in textbooks and reference books available. PSpice is a powerful general purpose analog circuit simulator that is used to verify analog or mixed digital circuit design and to predict the circuit behavior. Its simulation waveforms are nearly as same as the experimental waveforms. The overall working stages of Boost converter, especially the transient process from start to steady-state, are simulated and analyzed by PSpice in this paper. All the stages of store energy element of Boost converter are also introduced. Some simulation waveforms are given to verify the analysis. Thus the understanding of Boost converter for designers is deepened.