Dewatering is one of the most common and most effective methods to minimize the adverse impacts of the ground water adopted during the construction of the foundation pit works. During construction, proper parameters and suitable techniques are determined on basis of the geological conditions and actual situations of the works, so as to achieve satisfactory dewatering results. On basis of the engineering practice, the article presents the adverse impacts of the ground water on the deep foundation pit works, the methods of calculation of the dewatering parameters and the environmental control measures.