In view of the provincial grids complex structure， close connection between the elements， and difficulty in maintenance scheduling planning， a decision support system（DSS） based on rich Internet applications（RIA） technique is presented to monitor and dynamically display maintenance scheduling. The object-oriented method is adopted to abstract and describe the primary components characteristics of the electric power system. The RIA technique is used to display the whole electric power topological structure. More important， the DSS is capable of detecting thedetached islands” of automatic maintenance scheduling using the breadth-first search approach. Meanwhile， the incorrect maintenance arrangements detected will be automatically presented to users together with suggestions for correct and rational scheduling， effectively enhancing the accuracy and reliability of maintenance scheduling. The practicality and flexibility of the DSS proposed are verified in Yunnan power grid.