The invention provides a testing system of a transformer substation monitoring system and a method thereof. The testing system is capable of receiving monitoring information forwarded by a telecontroldevice through a simulation main station and issuing instructions according to the monitoring information, and is also capable of achieving a function of testing whether the monitoring information forwarded by the telecontrol device is right or not according to a regulation and control sequence table; in addition, the testing system is also capable of sending the simulation monitoring informationto the telecontrol device through a simulation substation, enabling a dispatching main station to achieve functions of receiving the monitoring information forwarded by the telecontrol device and issuing the instructions according to the monitoring information; meanwhile, the testing system is further capable of enabling the dispatching main station to achieve functions of configuring database ofthe dispatching main station, establishing a model and testing whether graphic image correlation is right or not so as to complete testing of the monitoring system. Through the testing system and themethod thereof, the testing process is separated by the simulation main station and the simulation substation, so that the contact between debugging staff and staff of the dispatching main station isomitted, and the testing time of the transformer substation monitoring system is reduced.