The invention belongs to the technical field of the access optimization of the flexible multi-state switches of distribution networks and relates to a two-step decision-making method for the optimal access of a flexible multi-state switch. The method comprises the following steps that: step 1, flexible multi-state switch access position preliminary screening indexes based on external characteristics are established, and the indexes are normalized and sorted; 2, a multi-index flexible multi-state switch optimal access comprehensive decision calculation model considering system reliability, voltage deviation and distributed power source acceptance capability is established; 3, system reliability is evaluated based on a power flow equation and a constraint condition which are satisfied by theoperation optimization of the flexible multi-state switch; and step 4, a grey correlation analysis-based multi-index decision model is established, a weight assigned value is determined, so that an optimal scheme can be finally determined. According to the method, the scientificity of decision making is improved through multi-index comprehensive decision making; two-stage decomposition is adopted, and therefore, a calculated quantity is reduced, and optimization efficiency is improved; and green, safe and sustainable power distribution network construction is effectively supported.