Abstract: This paper first introduces the complex network and the directed-weighted network method, and gives the formal description of the SA. Second, a metric method of SA complexity is proposed through SA edge weight, in-degree strength of component, out-degree strength of component, overall-degree strength of component and agglomeration of SA. Finally, an example is verified by the method given to metric the complexity of SA. The results shows that this method can metric the complexity of software system well based on strict formalization, and provides reference and support for subsequent development and maintenance of SA.