The article chooses an underground economical group of counterfeited cigarette in Zengcun, a country in Hebei Province, as a critical case and tries to analyze some theories about social network, especially those questions never be studied deeply before, such as how to build or maintain social network. Some main points can be generalized as follows: social network has its base and limit-things and any changes of things will transfer the size of social network. So social network in economic life is actually a whole dynamic process including building expanding and shrinking.
