This ex post facto research, conducted at SDN Gedong 06 Pagi, Gedong village, East Jakarta in August 2013, aimed to obtain empirical data of the influence of the intensity of playing on-line games towards the aggressiveness of grade II SD. Samples were taken using the technique of cluster random sampling and simple random sampling. The data were collected using question form and analyzed employing one way analysis of Variance (ANAVA) and t-test. The results of the testing of hypotheses using ANAVA indicate different aggression of the children in the three groups of intensity playing on-line game. T- test indicates all H0 rejected but Ha accepted. The implication of this research result is the intensity performed by the children in playing on-line games could contribute to their aggression against the environment. The role and efforts of teachers and parents in providing the children with educational games, can develop pro-social behavior and positive character of the children.