The invention relates to an improved PMU optimal configuration integer linear programming method. The method comprises steps that, whether the complete network state is completely observable is determined; whether a definition 1 is selected is determined; a PMU configuration model based on the definition 1 is established; a PMU configuration model based on a definition 2 is established; a posteriori algorithm under the definition 2 is carried out; a PMU configuration algorithm with no zero injection node is carried out; a PMU configuration algorithm with a zero injection node is carried out; and a posteriori algorithm is carried out on the condition that the zero injection node exists and the network state is unobservable. According to the method, when the complete network is observable, the condition with zero node injection or known node injection can be simply and accurately processed, and the optimal solution with the smallest PMU quantity and largest redundancy can be acquired; on the condition that the whole network state is not completely observable, according to different situations, the optimal solution which satisfies unobservable depth requirements and realizes the smallest PMU quantity can be acquired in relatively short time, and a new solution scheme is provided for solving PMU optimization configuration problems of observable systems and unobservable systems.