As it is full of inaccuracy in the world, people are required to make judgment under every condition. Accurate judgments could help people have a better understanding of themselves and the environment or their competitors, so that people could make wise choices or decisions. However, lots of researches found human judgments are inaccurate. Furthermore, people nearly have no sober awareness of this phenomenon. Studies from different disciplines attempt to explain this phenomenon. Among these explanations, the viewpoints from Evolutionary Psychology and Brain Science were most intriguing and original. Theoretical explanation from Evolutionary Psychology focused on the evolutional adaptability of inaccurate judgments in endless natural selection history, whereas the findings in Brain Science revealed the neurobiological basis corresponding to inaccurate judgments. Evolutionary Psychologists argued that many “misbelieves” are not accidental deviation or evolutionary design limitations, and that the reason why these “misbelieves” can be preserved is that they reduce the survival cost of humans and make individuals have more disposable resources or promote their physical and mental health, which would help humans meet the adaptive requirement of natural selection. For example, overestimation of oneself could make individuals more confident and more attractive in interpersonal relationships and group systems, thus they would possess more opportunities to take on the role and also get more trust of others around. Individuals like this kind would show evident advantages in the union, the status of competition, mate selection and other social activities. According to the error management theory of evolutionary psychology, there exists "deception" in the person's thoughts and actions is system error rather than random, and this error subconsciously make the most advantageous to the individual in the face of the uncertain situation choices, so that if a patient has "positive illusion", this would enable him to avoid falling into despair, and on the contrary, his health would be in a positive state as expected. One recent empirical research in Evolutionary Psychology used mathematical models to prove the advantages of "overconfidence" in context of competition for resources and agent-based model also confirmed that such a biased judgment strategy is effective in the war conflict. Taking advantage of technologies such as fMRI, ERP and TMS, Brain Science researchers found that part of the region and the structure in prefrontal cortex correspond to the inaccurate judgment, based on the results of experiments on normal and brain injury patients which involved perceptional, memorial judgments. For example, individuals’ self excessive judgment significantly reduced when applying TMS in the medial prefrontal cortex (MPFC) of them; fMRI study found that the activities of the activities in dorsolateral prefrontal cortex (DLPFC) enhanced especially when subjective judgment and objective results match. Future research should pay attention to how to carry out researches on inaccurate judgments from evolutional developmental perspective and how to achieve clinical application of cognitive neuroscience findings in order to improve judgments.