Abstract: Abstract: Recognizing the evolution and transformation progress of rural farmland under different terrain conditions is the basis of modernization management of agriculture, which will also help the targeted poverty alleviation in rural areas. Remote sensing and GIS (geographic information system) technology were used to analyze the farmland use in national-level poverty-stricken county of Horqin Left Wing Rear Banner in the flat area and Youyang County in the mountainous area. The analysis mainly focused on the variation of the quantity, quality, spatial distribution, configuration characteristic, distribution of topographic region and planting structure of farmland land from 2001 to 2015 when there is an enormous amount of migration from rural to urban areas. The results are as follows: 1) Compared with the mountainous county, the farmland per capita labor is more abundant in the plain county, but continuous expansion of farmland still occurs in the flat county while the shrink exists in the mountainous county. 2) The farmland quality of poverty-stricken county in the flat area is generally low and the inferior farmland changes obviously, by contrast, in the mountainous county, it is higher and the farmland of low and middle quality increases obviously. 3) The distribution of farmland in these 2 counties tended to cluster together; the farming radius in the flat county was expanding but it shrank in the mountainous county. The number of farmland patches and largest patch index increased in the flat county, while the number of farmland patches declined sharply and the largest patch index increased a little in the mountainous one. The mean patch size of farmland in the flat county was much larger than that in the mountainous county, but varying degrees were both increased. There was a raise of area-weighted patch fractal dimension of farmland in the flat county but a reduction in mountainous county. In the flat county, the low terrain niche range was the priority areas for development of farmland and there existed no significant change, while the middle-low terrain niche range was not the priority areas for development of farmland in the mountainous county. Meanwhile the advantage degree of farmland increased in the middle-low terrain niche range. 4) Generally, farmers in the flat counties prefer to plant food crops which are land-intensive agricultural products because of the man-earth relationship of wide land and few people, while commercial crops with greater weight are planted in mountainous county by contrast because of big population holding little tillable land. The results show that terrain and farmland resource are the critical factors influencing the difference of comparative advantage of regional production, which, to some extent, makes the pattern of farmland use and agricultural production various. Therefore, the investment and policy-making for agricultural modernization and targeted poverty alleviation must make the best use of the circumstances. The agricultural development mode in flat areas should change from extensive use of resources to protective utilization, so as to avoid the phenomenon of "land reclamation along with land desertification", which causes the soil desertification and the farmland quality decline. The development of agriculture in mountainous areas must change the traditional agricultural production mode to improve agriculture multifunction for the more value of "land economic output per unit area" through technological reformation and marketization.