Abstract: The sandwich enzyme-linked immunosorbent assay (ELISA) method was applied to measure contents of mCry 1Ac protein in different parts of the transgenic mCry 1Ac maize(Bt799) growing in the experiment field of the study at different growing stages. Results show that mCry 1Ac genes were expressed in leaves, stems, roots and seeds of the maize throughout the entire growth period, with the content of mCry 1Ac protein varying temporally and spatially in the range of (0.82±0.10) ~ (15.83±1.77) μg·g^-1; contents of mCry 1Ac protein in leaves, stalks and roots of the maize all displayed an increasing trend with growth of the plants, and reached the peak at the seed maturing stage; meanwhile, the content of mCry 1Ac protein in leaves remained the highest among the various plant organs at all the growing stages, except for the seedling stage, whereas the content in seeds was the lowest at the seed maturing stage, being (2.86±1.71) μg·g^-1.