Large scale foundation pit support and dewatering engineering were carried in complex geological conditions for BBA(BMW Brilliance Automotive Ltd.) Tiexi New Factory Office Building, several construction technologies and construction methods were used with high requirements on the quality of construction. Because the rich content of groundwater and high water level in the area, the excavation security was very important. By further study on the safety monitoring projects, strict foundation pit safety monitoring program was made to ensure the safety of the construction.