The present invention relates to an analysis method and analysis system that can accurately analyze the contents of coenzyme Q-10 and a 2-electron reduced form thereof in a specimen, in which human blood plasma as the specimen is mixed with isopropyl alcohol as a pretreatment and the coenzyme Q-10 and the 2-electron reduced form thereof are extracted to the isopropyl alcohol. Extracted liquid is stored at a temperature of 4.degree. C. until the analysis is performed. The extracted liquid as an analytical sample is analyzed by an analysis system provided with a liquid-sending mechanism, a switching mechanism, a concentration column, a separation column, a reduction column, an ultraviolet absorption detector, and an electrochemical detector.