The invention discloses a power grid voltage temporary drop weak region identification method and device. The method includes the following steps that: the fault type of each fault line is obtained, and a corresponding voltage equation is selected; the drop amplitude of a sensitive load access point which is caused by a head end point and tail end point fault of each fault line is solved according to the voltage equation, and a weak index vector corresponding to each fault line is calculated; and a weak region corresponding to each fault line is determined through using a golden section method and/or secant line iteration method and on the basis the numerical value of the weak index vector. According to the power grid voltage temporary drop weak region identification method and device of the invention, the corresponding voltage equation is selected, so that the drop amplitude of the sensitive load access point which is caused by any point fault of each fault line is calculated; the weak region corresponding to each fault line is determined through using the golden section method and/or secant line iteration method; and a golden section method and secant line iteration method-combined method can be adopted to calculate a critical point, and therefore, the voltage temporary drop weak region of a power grid can be determined.