The invention discloses a method for detecting working stages of a power grid and a detection device. The method includes the following steps that: characteristic quantities of a sample power grid in a preset time period are obtained, wherein the characteristic quantities at least comprise power grid numerical value characteristics and power grid technical characteristics, wherein the power grid numerical value characteristics are used for representing the load characteristics of the sample power grid, and the power grid technical characteristics are used for representing the architecture attributes of the sample power grid; and the preset time period is at least divided into four working stages, namely, an initial stage, a development stage, a post-development stage and a saturation stage according to the power grid numerical value characteristics and power grid technical characteristics; the current characteristic quantities of a target power grid to be detected are obtained, and the working stages of the target power grid to be detected are determined according to the current characteristic quantities. With the method and the detection device of the invention adopted, the technical problem that the working stages of power grids cannot be detected in the prior art can be solved.