本文所讨论的ＳＥＣＡＡＰ系统以南京第二机床厂所生产的数控车床主轴箱为研究对象，完整地实现了主轴箱部件装配工艺的自动设计。文中重点分析了该系统的原理与结构；讨论了装配工艺知识规则库的建立；提出了装配信息的描述方法；讨论了装配顺序的决策思想；介绍了装配工序图的自动生成方法。 The SECAAP system discussed in this paper takes the CNC lathe headstock produced by Nanjing No.2 Machine Tool Plant as the research object, and fully implements the automatic design of the assembly process of the spindle box components. In this paper, the principle and structure of the system are analyzed emphatically. The establishment of knowledge base of assembly process knowledge is discussed. The description method of assembly information is put forward. The decision-making of assembly sequence is discussed. The automatic generation method of assembly process diagram is introduced.