Background: In recent years, the scale of Chinese hospitals and the resources they occupy are in a situation of rapid expansion. Whether these resources are conducive to improving the quality of medical care remains to be studied. Methods: The DEA model and the panel regression model were used to analyze the slack resources status and to study the relationship between slack resources and the quality of medical care. Results: First, from 2015 to 2018, slack resources was on the rise in 23 hospitals, with a significant reduction in 2019. Second, low-risk mortality decreased from .014% to .003% when slack resources increased from 0 to about .225. However, the low-risk mortality rate increased to .086% when slack resources increased to about .577. Conclusions: There is an inverted U-shaped curve relationship between slack resources and the quality of medical care in public hospitals in China. A small number of slack resources in the hospital is conducive to the improvement of the quality of medical care, but when it increases to a certain amount, it will be detrimental to the quality of medical care.