After 1949, especially in recent 20 years, the number of Beijing’s residential building has increased rapidly. Such fast development also poses a great impact on the eco-environment. Generally, the methods of assessing the impact of buildings focus on the direct or local impact during the construction or using period. This article assesses the indirect impact of the building materials in a city’s scale using the Life Cycle Assessment method. According to the analysis result, we find that the increase rate of residential building’s impact is higher than that of building area. After the discussion, we owing this difference to the building structures and building materials.