Taking onion T-type cytoplasmic male sterile line‘ 8-43A’，maintainer line‘ 8-43B’and restorer line‘ 8-43-57C ’as material，using firefly luciferase enzyme testing technology，this paper analyzed the changes in ATP contents of buds at different growing stages，and studied the relationships between ATP contents of buds and T-type cytoplasmic male sterility in onion．The results showed that there were no significant differences between the ATP contents of maintainer and restorer lines throughout the entire development process of bud．While，the ATP content of CMS bud was very significantly lower than that of the maintainer and restorer lines，especially at early grain stage，which only took 1% of that in maintainer and restorer lines．ATP content of the CMS line at early grain stage decreased to less than 1/10 of those at tetrad stage，illustrating a large quantity of ATP was consumed after mononuclear stage．And an even important thing was there might be barriers in ATP generation．The ATP content of T-type CMS in onion was very significantly lower than that of the fertile lines might be the reason for male sterility.