The cascading failure mechanism is studied based on percolation theory combined with electrical properties to explore the fault development path. Firstly

a branch fault percolation probability model is built. By combining with the branch health degree index and importance index

the branch outage probability model is obtained

which could identify a fragile branch in normal operation state of the system and predict a fault branch in fault running state. Secondly

the comprehensive consequence index of the cascading failure path is established. Combined with the path probability

a path risk assessment model is built

which could diagnose and analyze the cascading failure path. Finally

the validity of this method is verified using an IEEE 39 bus system.