The content of Bt（Bacillus thuringiensis Berliner） toxin protein of two Bt transgenic maize was tested.The results showed that Bt toxin protein was detected in all the test organs and phase of the transgenic maize,but its contents varied significantly among different organs in different stages.The expression of Bt toxin protein in Bt transgenic maize decreased with advance of plant development.Among different organs,the highest Bt toxin protein content in the leaves,less in stem,and the least in root,seed and faliment.