With the " Chinese Dream” put forward, the study on the social mobility expectation of residents has attracted more and more attention from the academia. This paper studies the impact of opportunity inequality on the social mobility expectation of residents under the background of the government goal of achieving social fairness and justice.　　Opportunity inequality refers to the part of income inequality caused by environmental factors that are uncontrolled by individuals. Social mobility expectation is defined as a positive or negative psychological expectation by individuals for the flow of future social class based on the objective social environment. Although a lot of literature has revealed the importance of social mobility expectation in influencing human cognition, redistribution preferences and well-being, there are still few studies on the factors influencing social mobility expectation. This paper aims to explore the relationship between opportunity inequality, which is a relatively prominent institution and environment factor at present, and the social mobility expectation of residents. 　　We decompose the effects of opportunity inequality on the social mobility expectation of individuals into direct and indirect effects. The direct effect refers to that the current opportunity inequality plays an important role in affecting current economic environment that individuals face, such as entrepreneurship, employment and promotion opportunities, and then has a lasting impact on future social mobility expectation. The indirect effect refers to that the current opportunity inequality, combined with the governmental policy measures for achieving the goal of social fairness and justice, affects people’s expectation of the change in future opportunity inequality and then acts on social mobility expectation. The empirical results show that: the higher the current level of opportunity inequality is, the greater the upward social mobility expectation is. And this positive effect is more pronounced in the group with poorer family background, elder age, higher education level, or non-agricultural household registration. We argue that, in the context of the governmental goal of achieving social fairness and justice, the degree of future opportunity inequality is expected to decline. Thus the adverse result of the direct effect of the opportunity inequality is offset by indirect effect, leading to the seemingly counter-intuitive conclusion. The empirical results also prove the indirect effect to some extent. Therefore, compared with the current opportunity inequality, the expectation for the changes in future opportunity inequality has more pronounced impact on the expectation of social mobility. While implementing the fair policies, the governments should carry out necessary expectation management, in order to enhance people’s trust in government departments. This will allow people to remain optimistic about future reform policy, so as to maintain the current relatively good social mobility expectation of residents.