The real time simulation algorithm of intelligent substation is studied in this paper. We analyze the contradiction between the weak computing capability of field testing device and the huge calculation of simulation. A new portable simulation platform based on variable step-time test calculation is using intelligent electronic device’s protection delay of action, the imbalance of simulate calculation and the powerful performance of X86/X64 system. ThisSplatform spreadsSSthe huge computational of theSinstantaneousSmutation and solves the bottleneck of real-time computing in simulation system. It solves theSproblem ofSreal-time computationSof overtime. Combining the calculation method, the simulation system adopts the structure mode of the model calculation part and the real-time communication part completely independent operation.The real time simulation test of intelligent substation based on X86\X64 platform is realized. The portable simulation platform successfully runs in field test of actual substation.