The invention provides a layering equivalence method for reliability estimation of a distribution network, and the method comprises the following steps: firstly, inputting calculating data into a computer system and utilizing a computer to respectively calculate the equivalence reliability of a generation and transmission system, a transformer substation incoming line and a transformer substationprimary connecting line, thereby forming a volume state table of a transformer substation low-pressure side bus; and then utilizing a state enumeration method to perform the combined enumeration calculation on a bus volume state and a failure event of each element in the distribution network; and finally, calculating and outputting a power flow and a reliability index under a fault state. The layering equivalence method provided by the invention is used for calculating the reliability of the distribution network with an ordinary structure as well as the reliability of a complex distribution network influenced by the major network outage, and is used for overcoming the defects of the existing fault mode result analysis method, the existing portioning method, and the like. The model generality is better, thereby being beneficial to application and popularization. The layering equivalence method can be widely applied to the reliability estimation of a complex middle-voltage distribution network and is especially suitable for the reliability estimation of a 6-10kV distribution network.