Gasification is one of the important technologies to realize the transformation of coal from fuel to raw material and to promotethe clean and efficient utilization of coal. Entrained-flow gasification is currently the predominate gasification technology, and the stableoperation of gasifiers requires that the liquid slag must have good fluidity. The crystallization behavior of the slag can lead to decreasedflowability, resulting in abnormal shutdown of the gasifier, which is a major cause of abnormal shutdowns of gasifiers. The main crystallization characteristics were summarized and discussed that affected the fluidity of slag and the key to studying crystallization behavior: crystallization kinetics. Firstly, the methods of judging the crystallization mechanism based on crystallization behavior and selecting appropriate crystallization kinetics models were summarized. The principles and characteristics of different crystallization detection methodswere compared to obtain more accurate crystallization behavior data by selecting the appropriate crystallization behavior detection methodaccording to the research focus, facility characteristics and slag properties. Finally, the effects of chemical composition and operating conditions on crystallization behavior were summarized. Significant differences in the crystallization mechanisms between different crystals cause that the same chemical composition has different effects on the crystallization behavior of different crystals. When the chemical composition of the designated slag is within a specific phase region, the influence of chemical composition and operating conditionson crystallization behavior of the primary phase mineral becomes more regular, and the conclusions obtained can provide more accurate guidance for the regulation of crystallization behavior. Combining research results with phase diagrams or establishing simple and accessible predictive models can better guide the control of slag crystallization behavior. Currently, the study of crystallization behavior mainly relies on experimental methods. Future research could integrate phase-field simulation and molecular dynamics simulation, among other methods, to further explore the mechanisms of crystallization and examine the effects of factors such as temperature fields and flow fieldswithin gasifiers on crystallization characteristics.