Objective To explore the nurses’ cognition of busyness in intensive care unit (ICU), summarize the main busy scenes, and provide strategies for solving problems of busyness. Methods Nurses in three ICU departments of Shanghai Oriental Hospital were selected by purpose sampling method from September 2020 to January 2021. Face-to-face semi-structured in-depth interviews were conducted with nurses. The interview data were analyzed and thematically refined using the method of Colaizzi data analysis. Results A total of 10 nurses were interviewed, including 8 general nurses and 2 head nurses, all of whom were women. The cognition of busyness covered three elements: explosively increased workload, time pressure, and overwhelming information from multiple sources. Busy scenes included four themes: large amount of patients, critical conditions of patients, unstable conditions of patients, and frequent service transfer among different medical divisions. Conclusions According to the three elements of nurses’ cognition of busyness and scenes of it, nursing managers can put forward corresponding solutions. This can retain or attract more nurses to work in ICU and provide better services for patients.