The invention relates to a method for monitoring the internal and external overvoltage in a power distribution station based on the sample of a voltage transformer, which comprises the following steps: (1) each phrase voltage signal is collected by the voltage transformer; (2) each phrase voltage signal is sent into a digital signal processor as a sample voltage signal after signal conditioning, photoelectric isolation, and the processing by a analog-to-digital converter and a data buffer, and the digital signal processor can continuously process each phrase sample voltage signal at the sample point to obtain each phrase voltage sample value of each sample point; (3) the digital signal processor can make the comparison between each phrase voltage sample value and the preset voltage reference value and judge that whether the internal and external overvoltage exist or not; each phrase voltage sample value is sent into the storage area of the digital signal processor, the voltage signal is uploaded by a communication interface, and an upper computer records the waveform and the parameter of the transient overvoltage, monitors all the internal and external overvoltage generated in a power system, and records the generation process of the overvoltage on line completely and precisely. The method of the invention has the advantages of safety and practicality, as well as rather less equipment investment.