There are a lot of vast and narrow plain in the Qin-Ba mountain area of South Shaanxi Province, which is regarded as the essential things. For a long time, local people have worked hard to build their farm land by reconstructing the bank and have acquired great achievements. However much plain can not still get rid of flood rushing calamity, and some have been rushed and repaired once and again; others have been submerged under the mud and sand. Slope and steep land of the mountains is increasing decreased and the soil fertility drops year by year, during tens of years, the average farmland per people of South Shaanxi Province has dropped from more than 0.2 hm² to 0.067 hm², what is more, it has dropped to little than 670 m² in some counties. To protect the basic agriculture land, prolong the usable life of plains in the river, and keep a sustained development, based on a great number of investigation, this article investigated and analyzed the reason of the producing calamity, and then put forward a very good suggestion about repair plains in the river.