Abstract: Most genetically modified (GM) plants contain Cauliflower mosaic virus 35 S (CaMV35 S) promoter. So, whether the plants contain GM component can be discriminated by detecting the CaMV35 S promoter. In this study, the highly sensitive electrochemiluminescence-polymerase chain reaction (ECL-PCR) assay combined with two types of nucleic acid probes hybridization was applied to detect CaMV35 S promoter in tobaccos. The experiment results show that the CaMV35 S promoter can only be detected in GM tobaccos, thus, the GM tobaccos and the non-GM tobaccos can be clearly discriminated. The method may provide a new means for detection of GM plants due to its sensitivity, simplicity and high efficiency.