Projection of cutting hills, backfill ditch, creating land and building city in the loess plateau have attracted much attention from all fields. What environmental effects will be caused by large- scale reconstruction of the topography, landform, geological and hydrogeological conditions of the loess gully become a hot topic of discussion. Taking the construction of the north area of Yan’an new district as an example,through geological survey, surface geophysical prospecting, monitoring and simulation,the effects of geological environment, water environment, vegetation ecological environment,social economy and human environment are preliminary analyzed, and how to treat cutting hills to backfill ditch project from the perspective of global urbanization and the rise of post- modern cities is discussed. The research shows that the moderate and strict quality projection of cutting hills to backfill ditch and city- building expands the construction space, improves the urban environment, improves the quality of life, improves the basic social services, and is conducive to urban governance and development. At the same time, it is pointed out that cutting hills to backfill ditch has changed the spatial structure of the land and its utilization mode, which will have different effects on the cave culture and loess landscape culture, and that modern buildings in the north aera of the new district have sprung up. Faced with the newly formed giant geotechnical engineering bodies, it is also necessary to think about the dangers and deal with them scientifically, and construction in the altered sites should be classified and in an orderly manner, and monitoring should be strengthened. According to the principle of ecological priority, saving and intensive, strengthen the study of land and space planning, so as to achieve the overall planning of new cities and old cities, and coordinated utilization of underground and ground space.