A methodology is proposed to evaluate the mission reliability of TT&C scenarios by modeling and analyzing space tracking, telemetry and command (TT&C) system using extended object-oriented Petri nets (EOOPN). The formal definition, operational rules and the modeling approach were given. It can embody the object-oriented idea by introducing the concepts of public place, message arc and message handle function into the model, and it has good hierarchical structure and modularity. The EOOPN model can completely describe the TT&C system composite and mission process and reflect the dynamic stochastic factors in system operation. After simulating the EOOPN model, the case study reveals that the simulation results have a good convergence, and the errors are controlled within one percent compared with the analytical result of Markov models, proving the effectiveness of the model.