In recent years, a subcategory of pathological internet use, named online game addiction, has aroused extensive attention from academic circles. The online gaming addiction shares many negative impacts of substance addiction, such as failing at school, breaking family relationship and social relationship. Nevertheless, there was fairly lack of psychophysiological investigation about the underlying mechanisms to support the characterization of excessive use of online gaming as behavioral addiction. To investigate whether the attentional bias plays a crucial role in the development and maintenance of excessive online gaming use, the authors obtained EEG data during a revised Stroop paradigm and during a color matching task using online game-related and neutral words in 12 online game addiction patients and 12 casual players. The behavioral data in the color matching task derived from both groups did not show a comparable interference effect associated with the online game-related words. However, based on the analysis of the ERP data, we found that the online game-related words elicited significantly large amplitudes of P200 and P300 when compared with the neutral words in the group of online game addiction patients, whereas there was no significant difference of that amplitudes between cues of the online game-related words and neutral words for the group of casual online game players. These ERP results are discussed that in online game addicts the meaning of the online game- related words would interfere with color matching, not only in an early, preconscious, automatic stage , but also in more conscious and controlled , motivation-related stage of attentional processing of information . The results indicated that the online game addicts were difficult to ignore the meaning of the colored words, and had to allocate more attention resources towards online game-related stimuli than to neutral stimuli. It can be concluded that online game addiction individuals display an enhanced attentional processing of online game-related stimuli, and this can be regarded as an expression of a greater responsiveness to online game cues. The present study was to investigate the time-course and cognitive mechanism of online game addiction, demonstrating that the enhanced online game cue-reactivity may play an important role in the maintenance of the problematic internet use. In the current environment of abundant online game resources, the tendency to excessively use online game will continue.