Abstract: With the recursive traversal，non-recursion traversal and level traversal methods of BOM（Bill Of Material） and its wide
use of multi-level generic pieces and complex structure，this paper proposed an improved algorithm checking the overlaped nest and the legitimacy，which integrated the basic theory of DAG（Directed Acyclic Graph） chart and the practical net structure of BOM.This paper used the idea of top-down and layers decomposition，designed different signs and iteration to determine the current operation target，maked full use of the operation features in relational database，freed from memory constraints，the algorithm has a higher efficiency in implementation.

Key words: Bill Of Material（BOM）, traversal method, overlaped nesting check, multi-level generic pieces

摘要： 结合物料清单（BOM）递归遍历、非递归遍历和层次遍历方法，针对多层次通用件的广泛适用构成的复杂产品，将实用性较强的网状BOM构造方法和无向无环图（DAG）的基本理论相融合，提出了一种新的BOM嵌套检查及合法性检查改进算法。该算法采用自顶向下方式逐层分解，设计不同的标志位及迭代来决定当前操作对象，充分利用关系数据库的操作特点，不受内存限制，具有较高的执行效率。

关键词: 物料清单, 遍历方法, 嵌套检查, 多层次通用件