Abstract: The complexity of large-scale software systems makes their structure more and more intricate, which seriously affects the quality of the whole systems. In order to master the sophisticated structure of software systems and control the structural complexity, a measuring method for complexity of software systems based on the basic structure of the system was proposed. According to the algorithms of extracting and expanding the software-core structure, the inheritance depths of classes are analyzed. Furthermore, a complexity metric method for large-scale software systems is discussed in the view of inheritance. According to the relationship between the depth of inheritance and in-degree of class, a method of detecting the structural drawbacks in a software system is proposed, by which defects in the structure can be diagnozed during the software designing, and the cost of testing and maintenance in future can be reduced.