Mass hysteria or collective hysteria usually begins when an individual shows a hysteric manifestation in front of others in the same group who later contagiously acquire the same symptoms. The underlying pathogenesis of mass hysteria is still unknown. It has been demonstrated that the mirror neuron system (MNS) provides an important neural substrate for humans' ability to imitate and there is an inhibitive component of MNS keeping us from imitating everything we see. We proposed that the inhibitive component for MNS automatic imitation may not function well in individuals of the group that results in the outbreaks of mass hysteria. We also provide evidences from emotional contagion, gender difference and treatment in mass hysteria to support this hypothesis.