Abstract: Through studying marginalization of the arable land in Lanzhou City, integrate method of marginalization of the arable land, the author sought out new research ideas for interpretation of land use/land cover change of Lanzhou City. Based on the essence and the diagnosis standard definition of the marginalization of arable land, using the data of Lanzhou statistical yearbook and the costs and returns account of agricultural products in Lanzhou from 1990 to 2010, the author diagnosed the marginalization phenomena of cultivated land use in China. The results showed that: there were once obvious marginalization phenomenon and two times suspicious marginalization evidences of the cultivated land utilization in the last two decades in Lanzhou. The first suspicious marginalization evidence of the cultivated land utilization was from 1990 to 1992. The obvious marginalization phenomenon was between 1995 and 2002, but the one was the longest and more serious. The following suspicious marginalization evidence of the cultivated land utilization from 2004 to 2005 was détente and short time. In the marginalization of the arable land under the laws, the marked decline of the degree of intensity of the cultivated land use. Theory of the marginalization of arable land use was useful to explain the changes of arable land use in China.