Expert systems are computer-based systems that use knowledge, facts and reasoning techniques to solve problems that can usually be solved only by an expert in a particular field. Salmonella is the main bacterial cause of food-borne diseases. In general, serotypes of Salmonella cause disease in the gastrointestinal organs, infection of Salmonella bacteria can attack the digestive tract that includes the stomach, small intestine, and colon. Diseases caused by Salmonella bacteria are typhoid or typhoid fever, diarrhea, and dysentery. There are still many peopl\e who do not know the symptoms of this bacterial infection and how to diagnose with a high degree of certainty. To be able to know the level of certainty of bacterial infection this researcher use the Dempster-Shafer method. This method is used to calculate the confidence value of the patient's selected symptoms by comparing each weighted value of the two initial symptoms selected for later than the weight value of other symptoms, resulting in new symptoms advocating a disease with the value degree of certainty or belief. The result of this research is to create an expert system application that can diagnose diseases caused by Salmonella bacteria as many as 3 types of diseases that are typhoid, diarrhea, and dysentery along with the solution or drug treatment and use Dempster Shafer method to get the trust value in the percentage of the disease diagnosis
