The invention discloses a method for regulating voltage of key node of grid polymerization based on measurement of a phasor measurement unit in a wide-area environment. The method is characterized by comprising the following steps: analyzing a relation between voltage vectors and current vectors of nodes, analyzing a relation between the voltage vectors of the nodes and power, regulating voltage of the key node of a polymerization grid in the wide-area environment, and solving a key node voltage regulating model by a nonlinear least square method. According to the method, the analytic relation between the voltage vectors of the nodes and the power is obtained by virtue of the relation between the voltage vectors and the current vectors of the grid nodes; the definition of grid polymerization and a regulation relation between the voltage vectors of the nodes and the power are obtained on the basis of the analytic relation in the wide-area measurement environment; a regulation equation for grid polymerization to the key node is further obtained without taking an out-of-limit power transmission circuit trend into account. The method is scientific and reasonable as well as simple and feasible, and is accurate in regulation, high in applicability and suitable for simplified analysis, on-line monitoring and real-time control of the grid.