Shyness is a very old topic, and it is also a topic with Chinese local cultural characteristics. Under the background of Chinese culture, shy individual was considered with behavioral features of social expectation, such as clever, obedient, easy-going, and modesty, and shy experience is also common in Chinese. However, with the rapid development of China's economy and society, the social adaptiveness with shyness become more negative, shyness or its generalization can lead to a series of internalizing and externalizing problems, and shyness has become a potential risk factor of social adaptation. Facial expression is an important carrier of mood message, which is also a mainly information source during the interpersonal interaction. Cognitive Theory Model has believed that the behavior of shy individual is correlation with cognitive biases to the facial expression. Some research have found that high shy children have stronger recognition ability and more sensitive to the anger facial expression, whereas some research have found that high and low shy children have no significant differences in recognition of six basic facial expression. These contradictory conclusions may be related to the usage of experimental materials, which typical facial expressions were used; And recognition accuracy were used as indicator which is insufficiently sensitive. In addition, sad facial expression is thought to trigger empathic responses which are associated with prosocial behavior. In order to further explore the cognitive biases of facial expressions in shy individuals, the current study investigated the differences of perception bias and perceptual sensitivity to ambiguous emotional facial expression between high and low shy children. In this research, we adopted the categorical perception emotion identification task, and ambiguous emotional facial expressions with happy-angry, and happy-sad continuum were used as experiment material, 29 high shy children and 30 low shy children were selected as the subjects from 918 pupils in 5 ~ 6 grade. The results showed that: (1)The category boundary of high shy children on happy-angry ambiguous emotional facial expression was significantly greater than that of low shy children (t(54)=3.28, p=.002, Cohen’s d =.88), which leaned to the happy endpoint, that is, high shy children perceived the shift later from which the expression category of angry to the happy, and tended to perceive the happy-angry ambiguous emotional facial expression as angry.(2)The category boundary of high shy children on happy-sad ambiguous emotional facial expression was significantly greater than that of low shy children (t(49)=2.29,p=.026,Cohen’s d =.64), namely, high shy children tended to perceive the happy- sad ambiguous emotional facial expression as sad. (3)There were no significant differences in the slope of happy-angry and happy-sad ambiguous emotional facial expression between high and low shy children. In conclusions, the high shy children had negative perception bias, including hostile attribution bias to the angry expression and higher sad empathy response to sad expression. In addition, they were insensitive to the shifts in the categories from happy to sad, as well from happy to angry. The results suggested that the intervention training by adjusting the category boundaries of facial expression for shy children can be carried out.