Purpose: This study evaluates the clinical judgment levels of nursing school students in simulation practice of diabetic ketoacidosis and score differences in clinical judgment levels based on academic record grades. Methods: The clinical judgment levels of 149 nursing students (3rd grade) who received a lecture on simulation practice for diabetic ketoacidosis simulation were evaluated during the period from March 3 to June 20, 2014. Data were collected and measured for the general characteristics, clinical judgment levels of nursing students in simulation of diabetic ketoacidosis, and difference in scores of clinical judgment levels according to grades. Results: Clinical judgment levels of these test participants was 2.82 points on average out of a full score of 4 points, and it was represented in the order of noticing (3.01), interpretation (2.86), response (2.79), and reflection (2.60) for each area. In addition, score differences in clinical judgment levels based on academic record grades were significantly higher in the upper ranks than in the lower ranks in all the areas. Conclusion: In simulation practice of this study, through observation by rubric education method, an objective recognition could be assessed and the importance of nursing knowledge was implied.