Acupoint is the basis of acupuncture. To elaborate the theory of acupuncture, the structure and function of acupoint should be clarified in advance. By exploring the discussion upon the classification, distribution and structure of acupoint in Huangdi Neijing (Inner Canon of Yellow Emperor), qi zheng lun (on meridian points and extra points), jie jiao lun (on convergence of joints) and guan ji lun (on three-dimensional structure of acupoint) are extracted. Based on whether located on the fixed sites, acupoints are classified into meridian points and extra points, while the meridian points are divided into 4 categories, i.e maishu, gukong, qixue and muxue. The convergence of joints illustrates the principal rule of acupoint distribution. The density of the major and key acupoints is proportional to the size and the complexity of function of joints. Acupoint is recognized as a three-dimensional structure in consideration of its external distribution on the body surface and the substances inside the body, which can be explored and examined. In addition, the relationship between meridian points and extra points, the significance of meridian points in different conditions, and the approaches to acupoint study are deeply discussed and analyzed. The crucial problems and the way for solving them are proposed for the future study to provide the references to the inheritance and innovation of acupuncture.
俞穴为针灸学的立足之本，要说明白针灸之理，必先明俞穴的结构与功能。通过发掘《黄帝内经》有关俞穴分类、分布、结构的论述，提炼出“奇正论”“节交论”“关机论”三论，指出俞穴按有无固定位置分为“经俞”和“奇俞”两大类，经俞又分为脉俞、骨空、气穴、募穴四类；俞穴分布总规律是在“节之交”，俞穴特别是大俞要穴分布的密度与关节大小及其功能的复杂度呈正比；俞穴是一内有“机”外有“关”的立体结构，其“机”在脉会中，而“脉会”可探寻可考量。另就经俞与奇俞的关系、经俞不同状态的意义，以及俞穴研究的路径选择等问题进行了深入的讨论和分析，提出未来俞穴研究急需解决的关键问题及解题思路，以供针灸学守正创新之参考。.
Keywords: acupoints; acupuncture; classification; rule of distribution; structure.