耕地资源是国计民生的根本，随着人口数目的增长和社会经济的发展对农产品需求有增加，要保证国家粮食安全和社会稳定，必须留有足够数量和较高质量的耕地。北京作为华北地区重要的中心城市现阶段的实际情况是：建设占用的多是灌溉设施、基础设施均较好的优质农田，而新开垦的耕地多位于偏远、贫瘠之地，补充耕地的质量远低于被占用的耕地质量，表现出仅数量上而非质量上的平衡，背离了耕地占补的目标。耕地上这种占优补劣的现象根本原因在于目前没有规定补充耕地质量的量化指标，土地行政主管部门和农业行政主管部门在具体监督和管理过程中，不能判断补充耕地的质量情况，这种质量上的平衡存在着时间差和空间差，在质量平衡上可操作性比较差。为此，国家和北京市都出台了很多政策，采取有效措施对耕地进行保护，起到了一定的作用。然而，由于多种原因，特别是耕地质量测算问题，维护耕地总量平衡停留在数量平衡层面上的问题并没有得到有效的解决。而数量-质量型平衡是实现耕地总量动态平衡的关键所在。补充耕地数量质量按等级折算，是按照农业综合生产能力不降低的原则，利用农用地分等的成果和方法，将补充耕地数量、质量与被占用的耕地等级挂钩并进行折算，实现耕地的占补数量和质量平衡。本研究以北京为例，基于北京市土地利用和耕地后备资源现状分析基础上，根据农地分等与耕地占补平衡之间的内在联系，借鉴农用地分等的方法，创建北京市农用地质量等别序列和补充耕地质量评价的指标体系和方法，探索分等成果与耕地占补平衡之间的嫁接渠道，从而建立北京市耕地数量质量的折算方法和折算系数，为耕地占补平衡中耕地质量测算工作充分合理的利用分等成果，推动北京市耕地占补由数量型向质数量-质量型升级提供参考。

Cultivated land resources is fundamental to the national economy and the people's livelihood,with the increasing of the number of the population and development of the economy, agricultural commodities are demanded rapidly.In order to insure the national food security and social stabability, it must remain enough quantity and better quality cultivated land. However, the practical situation of Beijing the captical of China is that the occupied cultivated land for building always being good quality land with better irrigation facility and infrastructure,while most of the reclaimed arable land is located in the remote and impoverishment place. The quality of the supplementary land is worse than the occupied land.It shows us the balance of quantity not but the quality which deviate from target of the balance for acquisition of cultivated land.This phenomenon happened mainly because of lacking the quantized index for the supplementary land,the state’s competend departments in charge of land resources and agriculture can not judge the quality of the supplementary land when they exercise the administration authority.And the balance of the cultivated land exsists the time and space differences so that operating availability is not so good.It is for this reason that the government have issued some unveil fresh policy and carried out a lot of effectual measures.But because of some reasons especially for the problem in reckoning the quality of the cultivated land, maintaining the cultivated land amounts balance still stay on the land quantity balance not but on the quality balance.And the quantity-quality balance is the key for maintaining the cultivated land amounts balance.The quantity-quality convert of supplementary cultivated land is in accordance with the agricultural synthesized production capability,making use of the method and results of agricultural land grading,linking and converting the quantity and quality of the supplementary cultivated land with grade of the occupied land,making the acquisition and compensation cultivated land coming to the quantity and quality balance. The article chose Beijing as a research sample region. According to the agricultural land grading results and cultivated land acquisition-compensation internal connection, the article is taking advantage of the agricurtural grading method, building up the agricultural land quality grade and the method and indexes of the evaluation of supplementary cultivated land. Then It could find out the channel between the agricultural land grading results and the acquisition-compensation balance and build up the convert meothd and index of beijing. This could promote the cultivated land acqusiton-cmpensation balance to upgrade from quantity balance to quantity-quality balance.