Abstract: In order to achieve the destination that both quality and quantity of the prime farmland are important in the demarcation of prime farmland. Taking Donggang, Liaoning province as an example，with the help of GIS technology, considering the viewpoint of natural conditions and site conditions, this paper selected the slope of land, scale, traffic location, the conditions of irrigation, land types which are adjacent to its suitability as evaluation factors to establish a demarcation method for prime farmland with the principle of grading according to quality based on land evaluation. The results indicated that the cultivated lands in Donggang with evaluation scores above 90 points were less, which only accounted for 23.73% of total cultivated lands and scattered in the whole area irregularly. The farmlands with evaluation scores above 70 points were the ideal prime farmland protection areas, which could make protection ratio of basic farmland meet the national requirement indicators. The empirical research shows that the method can reduce disturbances of human factors in the demarcation of prime farmland and make the demarcation of prime farmland more scientific and reasonable.