The invention relates to a method for identifying the parameter of a poor branch of a power system based on a multi-measured section Lagrange multiplier method, and belongs to the technical fields of power system scheduling automation and power grid simulation. The method comprises the following steps of: reading in a plurality of measured sections from a historical database one by one; establishing a state estimation model of each section, solving, and calculating the regularization Lagrange multiplier of each section; and accumulating the regularization Lagrange multiplier vector of each section to obtain a suspicious degree index of a branch parameter, namely the regularization Lagrange multiplier vectors of the plurality of sections. The method is convenient to implement; meanwhile, the accuracy of the original poor parameter identification program can be greatly improved.