In order to improve the nursing effect of respiratory critical illness, this paper combines the refined nursing method to explore the nursing plan of respiratory critical illness. Moreover, this paper uses the variable control method to explore the effects of nursing management, combines the hospital patient samples to conduct a controlled trial analysis, and conducts sample grouping according to the random grouping method. The patients in the control group are managed by traditional nursing management methods, the patients in the test group are managed by refined nursing management methods, and other conditions are basically the same. In addition, the experiment process variable control is carried out according to the mathematical statistics method, and the reasonable statistics and data processing are carried out. Through the comparison method, we can see that the refined management method proposed in this paper has a good effect in the nursing of respiratory critical illness.