The invention discloses a method and system for optimizing and analyzing reactive voltage, a reactive-voltage analyzing and evaluating platform of a provincial company, and reactive-voltage analyzing and evaluating platforms of a plurality of municipal companies communicating with the platform of the provincial company. The reactive-voltage analyzing and evaluating platform of the provincial company comprises: a main server communicating with a first web server and a first client, respectively, wherein the first web server is responsible for communicating with power management systems. Each reactive-voltage analyzing and evaluating platform of a municipal company includes a second web server, and a second client, wherein the second web server is responsible for communicating with main servers of power management systems and the provincial company.