The invention discloses a method and system of determining a transformer direct current biasing state with noise detection. The method comprises steps of detecting a noise signal at an assigned noise detection point of a transformer, and extracting a direct current biasing noise feature parameter according to the noise signal; and comparing the direct current biasing noise feature parameter with a preset direct current biasing noise feature parameter threshold, determining the transformer in a direct current biasing state if the direct current biasing noise feature parameter exceeds the direct current biasing noise feature parameter threshold, and otherwise, determining the transformer in a normal state. The system comprises a corresponding noise detection unit, a noise feature parameter extraction unit and a direct current biasing state determination unit. Equipment operation states are not needed to be changed, contact with live equipment is not required, the detection safety is high, and advantages of safety, accuracy, zero misjudgment, independence from sense organ determination and staff operation experience, convenient testing, and manpower and material saving are achieved.