It is systemic to expound how that the speculative behaviors are driven by the number of a series housing policies promulgated by China’s government for the real estate market. The market is resulted in full of speculative behaviors, and has been booming since the beginning of this decade, even though the market has only a very short history, How to rationally measure the speculative behaviors still remains open in the academe and practice. Based on the level of housing prices, this paper establishes some innovative dynamic models, proposes a concept of net mortgage loan to net speculative gain ratios to investigate the speculative behaviors and mortgage bubbles, and finally concludes some interesting results: The necessary condition of speculative behaviors’ existence is that the growth rate of housing prices must have a positive minimum boundary, and, the net mortgage loan to net speculative gain ratios subsequently exist, which approximately depict the potential risks banks would face. Furthermore, investor’s behaviors may impact the housing prices’ trend through changing the expectation or variance of housing returns in sale or resale massively. The last finding indicates that how investor’s behaviors change market’ behaviors, which evidently testifies that the efficient market hypothesis would be invalid.