Diagnosis for primary diarrhea and the reasons should be proved by medical record, symptom, physical sign, routine analysis especially stool test. Through careful analysis on medical record and rough results of tests above mentioned, accurate diagnosis usually can be received usually. If the diagnosis is not clear enough, then further X-rays barium enema, barium meal test and/or proctoscope and colonoscope test should be taken. If there is still no clear conclusion, then tests of visualization, such as ultrasonic, CT, Encoscopic Retrograde Cholangio-Pancreatography(ERCP) should be taken according to different condition to detect diseases on gallbladder and pancreas, or proceed experiment on digestive function of small intestine, breath test, biopsy of small intestine membrane can be taken to check if the digestive function of small intestine is good. Highly suspicious diseases like enteric tuberculosis, intestinal amebiasis etc. which cannot be diagnosed after tests, can be taken to treatment experiment within certain period. ]]>