Due to growth of patients, overworking of medical staffs influences medical quality. The aim of this study was to improve the efficiency of diagnosis and avoid medical malpractice. Appling the medical records from a regional teaching hospital in Taiwan, this research made use of data mining to analyze the use pattern of medical order and examination items according to different diseases. The probability of medical order items was calculated according to three categories, including total hospital, divisions and doctor. The medical order system shows the medical items based on high executed items to improve the efficiency of medical processes.