The trial indicated that nitrate-reductase (NR) activity in leaves showed descending trend itself during the florescence of transgenic cotton Nucotn 33B, the protease activity and protein content showed increasing trend itself, nitrogen and amino acid content had positive correlation with NR activity. The content of toxin protein showed a saddle shape variety trend from budding to flourishing. The leaves NR activity and protease activity have been improved by DPC (mepiquat chloride) treatment and the content of leaves protein, amino acid and the total nitrogen have been increased. At the same time the toxin protein content has been heightened. Finally the boll weight and boll number per plant have been increased.