Guided by the thought of system integrity, complex behavior of computer network is thoroughly study based on complexity theory. Based on chaos theory complex behavior property of computer networks traffic with different time-scale is deeply researched, the result indicates the universe of the chaos and scale-free behavior in real computer networks. The network behavior evolvement model that correctly describes function mechanism of general real networks is presented, and formal description of the evolvement rules is implemented, the fluctuations formula of input traffic is also deducted. Based on the mean field model of network traffic, the dynamical properties of network traffic system is analyzed, and the condition of chaotic dynamical behavior is achieved under mean field hypothesis.