The invention discloses a BART algorithm and super-absorption wall-based reactive power optimization method for the voltage of a power grid. The method comprises the steps of obtaining a primary threshold-crossing mode tendency by using historical data, and establishing a BART-algorithm-based voltage threshold-crossing diagnosis model by utilizing characteristic factors to obtain system characteristics of a current node; establishing a Brown motion model of a voltage time sequence, analyzing characteristics of a motion model of a super-absorption wall of the current node, and carrying out self-learning on parameters; obtaining an operation rule instruction according to the analyzed characteristics of the motion model of the super-absorption wall of the node and current system data characteristics diagnosis results; writing the operation rule instruction into a power system simulation system for simulation in form of constant value, and performing trial running for instruction simulation to realize the constant value. According to the method, voltage and reactive power on the low-voltage side of a transformer are in an ideal low-grid loss state, a complex optimization model is not required to be solved in an optimization process, and the reactive power is flexibly adjusted under the condition of taking the influence of a load, the voltage and the reactive power into full account.