Bt corn is one of the large-scale commercialized GM crops being planted around the world. The debate surrounding the potential ecological risk of Bt corn is ongoing. Among these there are concerns over the photosynthesis and growth properties of corn hybrids with the Bt trait transferred from Bacillus thuringiensis. In order to learn the behave of transgenic Bt corn in South China a plot experiment was conducted in a greenhouse in South China Agricultural University. The experiment compared the photosynthesis and some growth characteristics of Bt corn 34B24 with its non-transgenic near isogenic line 34B23. From the experiment it can be found that because of the expression of Bt gene, Bt corn had no leaves damaged by corn borer (Ostrinia nubilalis) while its non-transgenic counterpart had many leaves damaged by corn borer. But Bt corn plant was also found some physiological and ecological changes. The difference of the internal CO２ concentration between Bt corn 34B24 and its near isogenic line 34B23 was not significant. In most stages Bt corns had higher transpiration rate and leaf stomatal conductance. In the late stage, the differences of transpiration rate and leaf stomatal conductance between 34B24 and 34B23 were significant. But the net photosynthesis rate of Bt corn 34B24 was smaller than that of 34B23, and in the late stage the difference was significant. Bt corn plant had slightly delay for the growth and development. Bt corn 34B24 were found slightly less leaves than its conventional near isogenic line 34B23 at every observation. Bt corns also had shorter plant height, smaller leaf area than 34B23. As to the underground property, Bt corn 34B24 had decreased root vigor. 34B24 also had less total root length, total root surface area, and average root diameter than its near isogenic line 34B23.