The invention discloses a distributed power supply site selection constant volume optimized method and belongs to the technical field of distributed generation. The distributed power supply site selection constant volume optimized method includes the following steps: firstly, allocating plans according to a power distribution network structure and capacity of the distributed power supply position, generating individual positional information, generating search groups and investigation groups according to an improved particle swarm optimization; conducting load flow calculation of plans corresponding to each individual in the search groups and the investigation groups, and calculating voltage and power value of each node; creating comprehensive evaluation index according to the principal component analysis, and calculating corresponding adaptation value according to the distribution network structure, the distributed power supply capacity, node voltage, power value and other parameters in each individual; regulating the positional information of the search groups according to the adaptation value, comparing the positional information of the search groups with the investigation groups, generating sub-groups, iterating repeatedly until obtaining the maximum iteration time, and treating the obtained optimal solution of the groups to be the optimal plan of the distributed power supply site selection constant volume.