周振鹤师曾经指出,县是中国历史上最稳定的政区。隋唐以后的县治比较清楚,明清时代的县界都可以研究,而在魏晋南北朝中国政区体系大转变之前的汉县则比较模糊。此间汉县的地理变化,如果不算改名的话,有四种情况:一、析出新县;二、省并;三、短距离迁治;四、长距离侨置。后三种变化的全部情况不一定为后代文献 Zhou Zhenhe pointed out that the county is the most stable administrative region in Chinese history. After the Sui and Tang dynasties, the county government was clearer, and county boundaries in the Ming and Qing dynasties could all be studied. However, Han county before the great transformation of China’s political system in the Wei, Jin and Northern and Southern Dynasties was rather vague. Here the geographical changes in Han County, if not renamed, there are four situations: First, the precipitation of a new county; Second, the provincial and provincial; Third, the relocation of short-range; Fourth, long-distance resettlement. All the latter three changes are not necessarily the case for future generations of literature