Traditionally diagnoses of diseases done manually by consultant with the expert or a physician. In general human can perform a major role to solve complex medical problems as an expert. Now as the population is increasing and the time has become more valuable for modern civilization they don't have time for an appointment to the physician, so expert systems were designed to recognize diseases at home or office by simply putting the symptoms and find out the recommended medicine and reduce the burden of hospitals. In this paper, a rule based expert system is designed with twelve rules to diagnoses diseases Measles, German Measles, Flu, Common Cold, Mumps, Chicken Pox, Whooping Cough, Meningitis, Diphtheria, Influenza, Typhoid Fever, Anaemia for provide good services in health.