The invention belongs to the monitoring field of electric equipment running states, and particularly relates to a spectrum system and a method for directly measuring the concentration of furfural in transformer oil. The spectrum system comprises a first optical lens, an absorbing pool, a second optical lens and an optical frame, and is ingenious in design, simple in structure, high in sensitivity and convenient to operate. Based on the spectrum system, the method for directly measuring the concentration of furfural in the transformer oil is provided. The spectrum system is adopted for determining the absorbance of the oil sample to be measured, so that the content of furfural in the oil sample to be measured is obtained; it is not needed to extract furfural in the oil, operation is easy and convenient, time and labor are saved, detecting results are real and reliable, the requirement for detecting furfural in the oil is met, heating is not needed during color developing, and therefore operation is easy and convenient.