In general, social class is a kind of social classification standard used to reflect the relative position of individuals in the social hierarchy. A person’s social class is defined as the objective social resources he controls (i.e. objective social class) and the level of his own social status he subjectively perceives (i.e. subjective social class). How to operationalize the concept of social class in psychological research? This is the first issue many researchers in this field have to face. Income (or property), occupation and education level are operational indicators commonly used in research to reflect the objective social class. But these three indicators, as the operational definition of objective social class, have certain defects. In terms of income and property, participants are usually reluctant to tell researchers their real levels. For occupations, individuals of the same occupation may have different social status. As for the level of education, people’s level of education is not always a good indicator of their actual social status. In short, all the three operational definitions are somewhat inadequate. Therefore, researchers sometimes measure multiple indicators at the same time and combine these scores into a total score of objective class. The operational definition of subjective class includes both questionnaire measurement and experimental manipulation. In addition to manipulating the participants’ subjective class, researchers sometimes also want to know the participants’ evaluation of other people’s social class and whether this perception of other people’s class will affect their psychological and behavioral results. Therefore, in such studies, researchers need to manipulate the social class of persons in their experimental materials. It can be seen that the operational indicators of social class is very complicated, so how to choose the appropriate operational definition in the study has become a problem. To this end, we put forward the following four suggestions. First, when considering the selection of operational indicators, it should be based on the research purpose and the hypothesized effects and mechanisms, and make clear which aspect of social class the research focuses on. Second, if we want to explore the effect of social class in general, we can consider using multiple operational definitions in the study. Third, it is not advisable to distinguish the social class level by selecting typical high-level and low-level class groups. Finally, we suggest that future researchers in this field should pay more attention to strengthening the reliability and validity of the empirical researches, and present more relevant information in the articles. Due to the complexity, there are still some problems to be further studied around the operational definition of social class. Future researchers should explore in depth the deviation between subjective class and objective class caused by class identification bias, as well as the inconsistency between static social class and dynamic social class caused by social class mobility. And the simplification of the effect of social class caused by sampling should also be further studied by researchers. In addition, it is also worth exploring to understand the differences between people’s definitions of social class with a cross-cultural perspective.