中文摘要：

基于对哀牢山是云南东西部自然界线的认识,对比分析哀牢山—元江河谷东西两侧5个纬度带、近几十年的重要自然要素、农业种植结构、农民收入来源及区域经济发展水平特征,结果表明：西部较东部地形高差较大、≤15°宜农土地比重较少、水汽和热量资源更丰富,形成东西部间显著自然环境差异;东部较西部的经济作物、旱作种植比重更高,表明东西部在农业生产结构方面存在明显分异,而各部的种植结构（以旱作种植比例为例）在各纬度间呈近纬向的相似性变化;东部较西部的人均农业产值、农民纯收入及人均GDP更高,表明东西部经济发展水平存在较大时空差异,而东西各部内则存在较好的相似性。从区域社会经济发展方面佐证了哀牢山作为云南东西部界线的存在。

英文摘要：

The Ailao Mountains were considered as the natural borderline between the east and the west of Yunnan for a long time. Are there any differences showed by social and economic elements between the two sides？ In view of this, in the region between 22°50＇-24°50＇N and 100°46＇-103°47＇E where the Ailao Mountains and the Yuanjiang-Red River Valley were mainly located, 10 counties along both sides of 5 sections with a distance of around 0.5 latitude each were considered as the research spots. Some factors, including natural conditions, economic development, farming structure and net income were contrasted and analyzed. The major research results were obtained in the following. （1） The height fall, land suitable for farming, rainfall and water resource in the west were bigger, less and richer than the ones in the east, showing that the natural condition had obvious differences between the two sides; （2） The farming structure, the planting proportions of cash crops and rainfed crops in the east were higher than the ones in the west, indicating that the farming structure between the east and the west had obvious differences, and the farming structure on each side had a similar changing tendency among the 5 latitude sections; （3） The economic development status, per capita GDP, output value of agriculture and net income of farmers in the east were much higher than the ones in the west, which proved that the development level and the developing tendency at the spatial and temporal scales between the two sides had larger differences, and on each side, they were more consistent. According to the above analysis, the Ailao Mountains-Yuanjiang River Valley was not only the natural borderline, but also the social-economic borderline in the region.