Abstract: Due to the particularity and complexity of the expansion and reconstruction of large-scale steel structure public buildings, the focus and difficulties of its expansion and reconstruction work are determined. This article takes the "Dongguan Citizen Service Center" expansion and reconstruction project as an example, mainly introduces the problem encountered during the decision-making phase, design phase, construction preparation phase, construction and acceptance phase, operation and maintenance management phase, and the methods of applying BIM technology to solve them.