The article probes into the approach to the interns' capability of clinical thinking and analyzing and solving problems by disscussing causes of gastrointestinal hemorrhage. Correct clinical thinking always comes from solid basis and clinical theory and knowledge, careful history taking, meticulous physical examination, rigorous logical thinking and constant summing up experiences and lessons. As a teacher, we should help interns develop clinical thinking ability during their whole peroid of medical education.Besides, theory should be combined with practice to prevent and correct vicious clinical thinking