Ordered tree model for wide-area distribution and complex structure system are proposed, which can effectivly realize the fault detection in real-time. Therefore, the characteristics of complex structure system is andyzed and the ordered tree model is built. Relationship is implemented among testing data, using measurement data from sensors and the correlation between orderly tree nodes. Data of the corresponding nodes are calculated according to the relationship between the measured and estimated values of the corresponding nodes. The judgment factors are estimated and fault detection of the complex system is determined. Simulation results demonstrate the proposed method can effectively detect fault and provide the theoretical basis for system maintenance.