In consumer generated media (CGM) site, such as YouTube and nicovideo, only few contents are viewed very much, but most contents are only viewed few times. Our research target CGM sites are nicovideo.jp and syosetu.com. Nicovideo.jp is a popular movie CGM site in Japan and syosetu.com is the largest novel CGM site in Japan. We already found that pageview distribution of contents in both CGM sites follow a lognormal distribution. In this paper, we consider user's content selection model which will lead lognormal distribution. We apply Geometric Brownian Motion model into SIR model. SIR model is used for simulation of population transition process or epidemic process of infection disease. In this paper, we report the results of some simulation.