The invention discloses a real-time simulation test method of a relay protection device. A computer can sample the quantity of external information through an external analog quantity and a digital quantity interface in real time to finish a closed-loop calculation of a target mathematical model while realizing the algorithmic calculation to the target mathematical model in a certain simulation time, meanwhile outputs calculation results. The invention changes an original mode of special detection equipment, achieves the real-time simulation function, and can output the calculating data in time through the hierarchic control. By the hierarchic control technology, the real-time transmission of large flow data is realized, meanwhile, information transmitted by a to-be-detected device can besampled back in real time, and the computer can carry out topological analysis and calculations based on signals.