Complex networks are the abstraction of the realistic world, and the transportation network is a complicated and huge system. Basing on the theories of complex networks and traditional epidemiological models such as SIR, SEIR. A new model is proposed to account for particular characteristics of the spreading of traffic congestion, which is analyzed in detail. This improved model, termed the Susceptible-Infected-Adjustive-Susceptible (SIAS) model, allows us to determine the best strategies to alleviate congestion. This dissertation, investigating the spreading rules of congestion in transportation networks, may yield both practical recommendations and new insights about the prevalence of congestion over the networks.