The invention discloses a method for determining a standard exceeding reason for factory boundary noise of a transformer substation. The method comprises the steps that a noise source of the transformer substation is divided into main equipment noise and fitting corona noise; factory boundary noise in the surrounding of the transformer substation is measured, and the standard exceeding range of the factory boundary noise of the transformer substation is determined; a measuring point position and an actually measured noise sound pressure level value within the boundary noise standard exceedingrange of the transformer substation are recorded; a sound pressure method is used to obtain the sound power of main equipment; a noise sound pressure calculation value of a monitoring point with the same position as the measuring point is calculated by adopting the actually measured sound power of the main equipment; and the actually measured noise sound pressure value is compared with the noise sound pressure calculation value to obtain a difference between the actually measured noise sound pressure value and the noise sound pressure calculation value, and the reason why boundary noise of thetransformer substation exceeds the standard is determined according to the difference. Thus, blank in a method for determining the reason why the transformer substation noise exceeds the standard atpresent is filled.