AimTo investigate the feasibility of the case mix index and compare the allocation of nursing human resources between two departments of a hospital with different case mix indexes in China. BackgroundThe case mix index is used to assess the resource allocation of all cases in two departments of a hospital. Its values can determine the resource allocation required to diagnose and treat the patients. MethodsClinical data were obtained from 23 different departments in 2015 and analysed retrospectively from October to November, 2016. Factors influencing the allocation of registered nurses were identified, and balanced quantities of patients with different case mix indexes were chosen from two departments. Spearman correlation analysis was performed. ResultsThe per capita nursing workload was significant (r=.669,p=.000). The length of hospital stay, quantity of nurses, and department case mix index were correlated with the nursingworkload (t=4.211, p=.000; t=2.962, p=.008; t=2.266, p=.035). Education levels (Z=-1.391, p=.164) and the professional titles (Z=-1.832, p=.067) of the nurses were not statistically significant, whereas the registered nurse level differed between two departments (Z=-2.125, p=.034). ConclusionThe case management index provides references for the efficient allocation of registered nurses in clinical practice.