The mechanism of aggression is always a hot topic in psychology. With the development of internet, online aggressive behavior has gradually become a new form of aggression. Now, it is anxious for college students to face traditional aggression and online aggressive behavior from different people. According to the previous researches, the rate of online aggressive behavior is 59.5% in China, and the aggression rate is nearly 88.8%. Exposuring to traditional aggression or online aggression may change personal emotions, behavior and cognition and finally making him aggressive, so it is necessary for researchers to find out which factors influencing traditional aggression or online aggression of college students. Among many influencing factors, alienation and cyber-ostraccism were believed to be strong predictors, so the purposes of the present study is to explore the relationship between cyber-ostraccism, alienation, traditional aggression and online aggressive behavior as well as the mechanism the effect of cyber-ostraccism on traditional aggression and online aggressive behavior of college students. There were 600 college students selected from different universities, with 301 males and 221 females, the range of the age is from 18 to 26 years old. The questionnaires included the Cyber- ostracism Questionnaire(COQ), Online Aggressive Behavior Scale(OABS), General Alienation Scale (GAS), and Chinese College Students’ Version of Buss-Perry Aggression Questionnaire (BPAQ-CCSV). We used Spss 24.0 and Mplus7.4 to analyze the data, and the Bias-Corrected Percentile Bootstrap method was used to analyze the role of alienation between cyber-ostracism and online aggressive behavior and traditional aggression. The results show that: (1) The relationships between each pair of cyber-ostracism, alienation online aggressive behavior and traditional aggression are correlated significantly and positively, the coefficient ranges .18 from .91 (p < .01); (2) The structural equation model (SEM) reveals that the data veries the theoretical model(χ2/df=3.28, CFI=.95, TLI=.94, SRMR=.04, RMSEA=.06); (3) Cyber-ostracism has?a?significant direct?effect on traditional aggression (β =.19, p < .001, 95% CI: .11~.28); Cyber-ostracism has?a?significant direct?effect on alienation (β =.44, p < .001, 95% CI: .34~.53); Alienation has?a?significant direct?effect on traditional aggression (β =.65, p < .001, 95% CI: .55~.74); Cyber-ostracism has?a?significant direct?effect on online aggressive behavior (β =.47, p < .001, 95% CI: .38~.57); Alienation has?a?significant direct?effect on online aggressive behavior (β =.19, p < .001, 95% CI: .08~.30); (4) Cyber-ostracism has a significant indirect effect on traditional aggression through alienation , and the confidence interval of 95% is [.19, .37], Cyber-ostracism has a significant indirect effect on online aggressive behavior through alienation, and the confidence interval of 95% is [.02, .09], that is, Cyber-ostracism has a significant direct effect on traditional aggression and online aggressive behavior, and alienation plays a partial mediating role among them. It is concluded that in the structural equation model (SEM) of cyber-ostraccism and online aggressive behavior and traditional aggression of college students, alienation plays a partial mediating role. These findings may contribute to a better way to solve the realistic problems of college students’ traditional aggression and online aggressive behavior. Moreover, it can provide us some constructive suggestions and measures to eradicate college students’traditional aggression and online aggressive behavior.