In this paper, we construct a theory to reasonably explain the formation and crash of assets bubbles under the situation when investors own the psychology of positive feedback and house money effect. The results of this study show that bubbles formation is caused by positive feedback trading behavior of those investors who are in search of trend, and the bubbles crash is related to house money effect of investors. The model we constructed can perfectly interpret the formation and the crash of assets bubbles. So, the description of the behavior of investors in this paper can be treated as a good reference for market participants when they are making investment decisions.