The gastrointestinal tract works by taking food, mechanically destroying, digesting, absorbing and disposing of undigested substances. For many gastrointestinal specialists, it is the second-largest human brain because it affects other organs and plays an important role in strengthening the body's immune system. Due to the importance of the gastrointestinal tract and its direct relationship with human daily life, timely diagnosis of this disease has a major role in the treatment and improvement of human beings. Major developments in diagnostic techniques during the past years have led to this update about indications for assortment and performance of currently available tests. So, this article presents an expert system for diagnosing the type of gastrointestinal disease and determining the type of tests needed to definitively diagnose the disease. The outputs of the expert system are designed according to the patient's symptoms. The VP-Expert shell is used to design this expert system. The results show that the designed expert system can be useful in cases where immediate access to the expert is not possible.