Human brain is a very complex network composed of billions of neurons, and each neuron in the cortex connects to more than 10,000 neurons via synapses.All kind of information are stored, transmitted and processed in the network and finally transformed into various commands to direct humans actions.So it is believed to be instructive to study the dynamical properties of neuronal networks for exploring the brain working mechanism.Although the real structure of the brain network is not clear yet, small-world connectivity has been found in some biological neuronal networks.Hence much attention has been paid on small-world neuronal networks.