When applying the fault enumeration method to evaluate the reliability of the whole transmission and distribution network composed of transmission network and flexible interconnected distribution network,apart from analyzing the influence of internal faults of the transmission network and distribution network on their respective power supply reliability,the interaction between the transmission network and distribution network should also be considered under the fault scenario. Based on existing independent reliability evaluation algorithms for the transmission network and distribution network,the reliability evaluation method for the whole transmission and distribution network is proposed in this paper. The proposed method in this paper can account for the interrelation between the operation states of the transmission network and the distribution network under the fault condition. The node load reduction after the failure of the transmission network is refined into the optimized load cutting scheme of the distribution network. While improving the accuracy of the reliability evaluation results of the transmission network,the load loss of the distribution network caused by the failure of the transmission network is included in the reliability evaluation of the distribution network. In addition,the load loss caused by internal faults of the distribution network and its influence on the reliability of the transmission network are included in the reliability evaluation of the transmission network. For the whole transmission and distribution network,the reliability index of the transmission and distribution network is calculated by the analytical method based on fault enumeration. The validity of the reliability evaluation model is verified by the results of the numerical analysis.