In order to detect the genetically modified plant components in food,three positive plasmids ppCaMV35S,ptNOS and ptCaMV35S as positive test controls were independently constructed,then two endogenous genes (pUbi,pRice-actin) and three regulatory genes(pCaMV35S,tNOS and tCaMV35S)were selected to detect the genetically modified components in four genetically modified crops (corn,rice,cotton and soybean) and two non-genetically modified crops(corn and wheat) using TaqMan real-time PCR.The result of specific test showed that the constructed positive plasmid could meet the actual detection needs, endogenous genes and other regulatory genes had good specificity.The limit of detection(LOD)of pCaMV35S and tNOS in transgenic cotton samples were 1 and 10 ng,respectively,which could effectively screen and test genetically modified crops and products that were commercialized or in the intermediate test stage.