The invention relates to a site selection constant-volume method and system for a w-voltage line voltage regulator. The method comprises: a low-voltage demarcation point and a distribution transformer of a target distribution network are identified to obtain a demarcation point distance between the low-voltage demarcation point and the distribution transformer; a line load type of the target distribution network is identified and a load increasing promotion coefficient of the target distribution network is set according to the line load type; on the basis of the demarcation point distance and the load increasing promotion coefficient, a mounting point distance of a low-voltage line voltage regulator is determined, and a mounting site of the low-voltage line voltage regulator is selected at a circumference by using the distribution transformer as a center of circle and the mounting point distance as a radius; and load nodes beyond the circumference by using the distribution transformer as the center of circle and the mounting point distance as the radius are identified to obtain a first selected load node, a total load capacity corresponding to the first selected load node is obtained, and a configuration capacity of the low-voltage line voltage regulator is determined based on the total load capacity and the load increasing promotion coefficient.