With the rapid development of the economy, carbon dioxide emissions also show an upward trend, and it is urgent to solve the problem of carbon emissions. With the support of Internet technology, the carbon emission monitoring and early warning system based on blockchain technology provides ideas and help to realize carbon peak and carbon neutral in China. Combined with the idea of green carbon emission, this paper skillfully combines the blockchain and the construction of the indicator system, borrows the carbon emission collection platform built by the blockchain technology, and constructs the carbon emission evaluation indicator system in line with the civil buildings. At the same time, it utilizes the hierarchical analysis method and the environmental quality model to make a comprehensive evaluation of the carbon emission of civil buildings; and applies it to a civil building in Harbin, which confirms the feasibility of the method.