Abstract: Based on the network theory’s capability to describe both the power-law distribution and the small-world effect in the social networks,the societal computing can measure the complex behavior in the society．Firstly the statistical method is proposed to distinguish two types of nodes with different active degrees through the character of the power-law distribution,which can be deployed as spam filter．Considering the small-world effect,the average distance between any two nodes changed lightly while the number of nodes varied significantly．The characters of different active nodes were validated in the spam filtering procedure from the original electrical mail records at last.

Key words: Social networks,Power-law distribution,Small-world effect,Spam filter