Abstract: Abstract: The high-standard prime farmland construction is an important measure to promote food production capacity on the background of land reclamation. Taking the new district of the north of Shenyang as study area, this paper constructed the synthesis system of farmland quality evaluation and site environment assessment under the guidance of LESA (Land Evaluation and Site Assessment) system idea for important farmland protection in America. The LESA system is composed of the LE system and SA system, which reflects the farmland quality by the result of LE evaluation and the suitability for social economy by the result of SA evaluation, and the site conditions include good and bad impact conditions. The land evaluation indices include natural indices such as slope, soil characteristics, and the site evaluation indices include social and economic indices such as urbanization, management efficiency and GDP (gross domestic product). In the evaluation process, suitability and unsuitability evaluation were separately carried out for high-standard prime farmland construction using the method of comprehensive contrastive analysis of several factors. Five suitable and unsuitable grades were classified by the natural breakpoint method with GIS (geographic information system) software. For the first 2 levels of suitability zone, the obvious characteristic was that the natural quality of farmland was superior to another 3 levels, which had better soil fertility including thicker soil layer, higher soil organic matter, better irrigation and drainage system. The LE result showed that these zones of good quality farmland were the most suitable for high-standard prime farmland construction, but when we considered the site conditions, some zones in the district were maybe not suitable, because some site conditions had negative impacts on the stability of high-standard prime farmland, which indicated that the evaluation of the site condition assessment was also needed. The unsuitability evaluation results showed that the farmland in the first 2levels of unsuitable zone had the highest risk of being occupied, and the site conditions included the pressure of urbanization, GDP and other social developing factors. Finally, 3 kinds of zones were planned including preferential construction area, conditional construction area and limited construction area. The results showed that there was 11 212.42 hm2 for preferential construction area, where the prime farmland had better quality and less pressure from social economy, and was distributed in the first and second grade of quality evaluation and the fourth grade of site environment assessment; there was 18 714.36 hm2 for conditional construction area, where the prime farmland had good quality and been influenced by site conditions, which was distributed in the second, third and fourth grade of quality evaluation and also the second, third and fourth grade of site environment assessment; there was 7 491.30 hm2 for limited construction area, where the prime farmland had different qualities and site conditions, which were that the prime farmland in the town surrounding was more influenced by site environment and had the risk for protection and using, while that far from the town surrounding had difficult conditions for using and improvement. The LESA system had a lot of advantages, which considered not only the good quality of farmland, but also the risk occupied by economic development demand, and the evaluation index was selected flexibly and could be adjusted according to different conditions, so the LESA system could be used in planning basic farmland, land planning, land reclamation and requisition-compensation of arable land and so on. In each place, when we used the LESA system, the selected evaluation indices must be suitable for the actual conditions, and we could refer to different advisories of different people or departments including agricultural experts, economic experts and other social managers. In this paper, it was also pointed out that the high-standard prime farmland construction should mainly consider the demand of large farming household, agricultural cooperative and family farm, combined with agriculture scale and industrialization business.