[Objective] The paper was to study the temporal and spatial dynamics of Bt protein expression in transgenic Bt cotton and to determine the inner relationship of Bt protein expression and transgenic Bt cotton. [Method] With transgenic cotton cultivar( GK19) as the test material,Bt protein contents in different organs,main stem functional leaves at different growth stages and different positions of main stem leaves at different growth stages were studied by enzyme-linked immunosorbent assay. [Result] There were differences in Bt protein content among different organs of transgenic Bt cotton; the Bt protein content of leaves at seedling stage was the highest,followed by flowers,bubs and bolls,and those of roots and stems were relatively low. The Bt protein content of main stem function leaves gradually decreased with the progressing development. There were great differences in Bt protein content among different positions of main stem leaves at different growth stages; the Bt protein content of the 1~(st)-7~(th) top leaves at seedling stage and full budding stage gradually decreased,while those at full flowering stage and full bolling stage first slowly increased then gradually stabilized. [Conclusion] Bt protein expression was found in all organs of transgenic cotton at all growth stages,and the expression level presented temporal and spatial dynamics. [Objective] The paper was to study the temporal and spatial dynamics of Bt protein expression in transgenic Bt cotton and determine the inner relationship of Bt protein expression and transgenic Bt cotton. [Method] With transgenic cotton cultivar (GK19) as the test material , Bt protein contents in different organs, main stem functional leaves at different growth stages and different positions of main stem leaves at different growth stages were studied by enzyme-linked immunosorbent assay. [Result] There were differences in Bt protein content among different organs of transgenic Bt cotton; the Bt protein content of leaves at seedling stage was the highest, followed by flowers, bubs and bolls, and those of roots and stems were relatively low. The Bt protein content of main stem function leaves gradually decreased with the progressing development There were great differences in Bt protein content among different positions of main stem leaves at different growth stages; the Bt protein conte nt of the 1 ~ (st) -7 ~ (th) top leaves at seedling stage and full budding stage gradually decreased, while those at full flowering stage and full bolling stage first slowly increased then gradually stabilized. [Conclusion] Bt protein expression was found in all organs of transgenic cotton at all growth stages, and the expression level presented temporal and spatial dynamics.