Microplastic pollution has become a worldwide issue. The discharge of sewage treatment plants (STPs) or wastewater treatment plant (WWTPs) is an important way for microplastics to enter the environment. This study reviewed the sources and occurrence characteristics (type, size, color and components) of microplastics in domestic and foreign sewage plants. It elaborated the removal principles of microplastics by primary, secondary and tertiary treatments. In addition, the removal effects of various treatment units and different processes on microplastics were summarized. In the future, the removal mechanism of microplastics in sewage treatment plants should be discussed in more depth, so as to further improve the removal rate of microplastics by optimizing and transforming traditional sewage treatment processes. Therefore, it is necessary to develop new technologies/processes specifically for the removal of microplastics and promote them to practical applications.