Code smells are low-quality code snippets that are in urgent need of refactoring. Code smell is a research hotspot in software engineering, with many related research topics, large time span, and rich research results. To sort out the relevant research approach and results, analyze the research hotspots, and predict the future research directions, this study systematically analyzes and classifies 339 papers related to code smell published from 1990 to June 2020. The development trend of code smells is analyzed and counted, the mainstream and hot spots of related research are quantitatively revealed, the key code smells concerned by the academia are identified, and also the differences of concerns between industry and academia are studied.