The invention relates to a three-phase power distribution network observability analysis method based on a linear circuit, and belongs to the technical field of power system dispatching automation and power grid simulation. The method comprises the steps: firstly completing the modeling of various types of measurement of a three-phase power distribution network; secondly obtaining an unobservable branch circuit in a three-phase system based on the rank analysis of a measurement Jacobi matrix; and finally obtaining an observable island of the system according to an observability analysis result of the branch circuit. The method can achieve the linear voltage measurement and power measurement of triangular connection, can achieve the processing of the impact on the observability from a distributed power supply, and can achieve the processing of the observability analysis of a power distribution transformer level.