Study on complex system based on the brittleness

The research on the basic characteristics of complex system has been done in this paper, in which brittleness as one of them is presented. Meanwhile, according to the theory of set pairing, concepts of brittle link function, brittle link entropy and basic element are defined. Finally, on the basis of data from the country from April to May, taking Beijing, and Neimenggu as examples, analysis have been carried out on the Severe Acute Respiratory Syndrome (SARS) based on the theory of brittleness. The results of simulation show that brittle entropy increase and brittle entropy of subsystems tend to ascend at the beginning of SARS interference. After the subsystems obtain the negative entropy from the environment, the entropy will be decreased. Effective methods are the key factor of controlling the spread of SARS.