Abstract: The design principle and realization method of the Computer Graphics Aided Operation Ticket Making System of Transformer Substation（CGAOT） are introduced．The operator can directly describe the circuit diagram of apparatus in a transformer substation using graphic tools provided by CGAOT ，and conveniently change the status of the apparatus just using mouse and real-time monitored control system．At the same time，the CGAOT can make out a series of operation sentences to form an operation ticket．The CGAOT can simulate the process of execution using the operation ticket，and also has the function to prevent mistake．The system will alarm when the operator tries to change the status of an apparatus that disobeys the previous setting of the logic relation of the operation sequence．This guarantees the safely running of the transformer substation．