This dissertation classifies sample patients by a measure of K-DRG to identify the most frequent group. and investigates the differences in the dependency of nursing by patient classification system in the SICU of Seoul National University Hospital in Korea. It also calculates the mean nursing care hours and costs per craniotomy patient, who is shown to be the most frequent patient group. The results of the research can be used as basic data for the development of relevant nursing cost system in the future. The results of the research are as follows: 1. Using data from 97 sample patients, as many as 26 groups are identified when the patients are classified by K-DRG. KDRG-001 (craniotomy) is found to be the most frequent group(43.30%). 2. The result from patient classification system grouping in craniotomy patients shows homogeneity in terms of dependency of nursing with 35 patients in the 4th group, 145 patients(74.36%) are in the 5th group. and 15 patients are in the 6th group among the total 195 sample patients. 3. The direct nursing care hours for the 4th, 5th, and 6th patient classification system groups are found to be 381 minuites. 483 minuites, and 519 minuites, respectively, which shows that the nursing care hours increases as the dependency of nursing is intensified. The indirect nursing care hours are found to be 454 minuites(7.57 hours). The total mean nursing care hours, which is the sum of the direct nursing care hours(467 min.: 7.78 hours) and the indirect nursing care hours (454 min.: 7.57 hours), is 921 minuites(15.35 hours) per patient a day. 4. The nursing care cost is calculated to be 123,297 won per patient a day. Considering the average duration in the ICU, we can find the total nursing care cost is 610,318 won.