Biological retention technology mainly through the matrix filtration, adsorption and microbial action to purify the infiltration of runoff rainwater. Because it can temporarily store the rain and then slowly into the surrounding soil, therefore, can play to reduce the surface rainwater peak flow, reduce runoff pollution and so on. Biological retention technology can include many forms, the more commonly used biological retention pool, concave green space, ecological grass ditch, plant buffer zone, rain garden and ecological wetlands. It can also include rainwater reuse facilities, soil improvement and so on.