In a narrow sense, it refers to those building materials that are nontoxic, harmless, pollution-free and do not affect the safety of people and the environment. In a broad sense, it refers to non-toxic and pollution-free building materials produced by using cleaner production technology, using less natural resources and energy, and using a large number of industrial or urban solid wastes, which are beneficial to human health. That is to say, green building materials not only need to meet the health requirements during use, but also need to meet the environmental protection requirements and "green" standards during production, reuse and disposal, which is obviously different from other building materials.