To analyze the dynamic behavior and the propagation mechanism of cascading failures in complex electric power networks，a novel hidden cascading probability model is proposed，which considers overload faults and hidden faults comprehensively in the electric power system based on the complex network theory.For the overload adjacent nodes in the model，both the nodes whose load change rate is biggest and the nodes whose load fluctuation is biggest in every cascading process are assumed to be the nodes prone to hidden faults.And then the simulations are executed on both the IEEE300-bus network and the Watts-Strogatz network.The simulation results show that the hidden faults in electric power system can aggravate the spread of the fault，and the spread range of the hidden faults will become appreciably wider with the increment of Watts-Strogatz network reconnected probability.Finally，it is pointed out that the methods of reducing the probability of hidden fault，reducing the edges reconnected probability in the small world network，and preventing power grids from evolving toward the random network，are effective ways to restrain the hidden faults propagation in cascading failures，and improve the safe performance of the electric power system.