In the test of dissolved gas components in insulating oil, if the oil sample has been degassed but the test failed due to other reasons, the principle of the distribution of each gas component in the oil can be applied to calculate component content. The degassed oil sample is filled with blank balance gas and tested again. After the test results are corrected, the original concentration of each component in the oil sample can be obtained. This method simple and reliable, reduced the trouble of repeated sampling.