Abstract: During the past decades of urbanization，there has been a continuing increase of mobility of our society. As a result，the left- behind children，many of whom are now becoming emerging adults，has become a group of the population that cannot be ignored. Left-behind children’s risk-taking tendency and actions may result in serious consequence in various aspects of individual or collective life，including sense of security and security behavior，healthy behavior and habit，sexual behavior，financial management，and social relationships. Focusing on the topic of risk- taking tendency and from the perspective of uncertainty cognition，this paper sought to summarize the existing research findings using the framework of the cognitive schema of uncertainty. The cognitive schema of uncertainty is a basic cognitive structure concerning the predictability of other people and the surrounding world，which is forming in the process of growing up in an uncertain family or community. The cognition of predictability of attachment figures （parents or companions） and events they experienced mediates an array of sequences， including heightened impulsivity，lower ability of delayed gratification，increased aggression and harmful behaviors，and emotional problems.

Key words: left- behind children, left- behind experience, uncertainty schema, risk- taking, migrant children