The invention discloses a method for field calibration of performance of a monitoring device for dissolved gas in transformer oil, wherein the method comprises the steps: preparing a first standard oil sample and a second standard oil sample according to components in the dissolved gas in the oil and the corresponding concentration range of each component; obtaining the concentration standard values respectively by using a high-precision gas chromatography analyzer; docking calibration interfaces of a first oil sample storage device and a second oil storage device with an on-line monitoring device, to obtain the concentration detection values respectively; obtaining the concentration measurement values respectively according to the concentration detection values; judging according to a measurement error of the on-line monitoring device according to relative errors and absolute errors; selecting the concentration detection value in the last continuous third preset time number thresholdvalue of preset gas in the second standard oil sample as the concentration measurement value of the preset gas; and calculating the relative standard deviation according to the concentration measurement value of the preset gas, and judging the performance of the on-line monitoring device according to the relative standard deviation.