Abstract: For casting in-site concrete buildings during construction, the dead loads of newly poured concrete slab and construction live loads are carried by time-dependent structures, which consist of early-age concrete structures and formwork system. The lack of understanding of the properties and design and analysis method for reinforced concrete buildings during construction results in high rate of quality problem and collapse during construction than that in service. Based on the concept that early-age concrete structures are the early-time form of building design production, which cannot be changed with construction progress, a design and analysis method for reinforced concrete structures during construction is proposed. Statistical parameters of construction error of formworks and construction loads are suggested based on site measurement, and examples are presented.