In this paper, a study on automation method for the circuit/EM (Electro-Magnetic) simulation is carried out to analyze effectively the SI/PI (Signal Integrity/Power Integrity) issues which occur on circuits and/or PCBs (Printed Circuit Boards). For the automation of the circuit/EM simulation, algorithms performing each process of the SI/PI analysis automatically (such as ports setup, circuit definition and SI/PI evaluation) are developed; thereby automation system for the SI/PI analysis is constructed with the algorithms. The automation of the circuit/EM simulation is accomplished in the environment of the C/S (Client/Server) architecture in order to reduce resources such as high cost computers demanded for the SI/PI analysis. The automation method for the SI/PI analyses proposed in this paper reduces effort, time, and cost spent on the environment setup for simulation and the SI/PI analysis process. In addition, the proposed method includes automation of the documenting process, which organizes, records and displays the SI/PI analysis results automatically for users.