Expert System is a part of Artificial Intelligence that contains the knowledge and experience put by many experts into a certain area of knowledge so that everyone can use it to solve specific problems. The implementation of expert systems is widely used in the health sector, for example by making diagnoses such as diagnosing nutritional levels. For example, diagnosing calcium levels in broccoli. Diagnosis is the process of examining something using certain methods and techniques. Diagnosis is done to explain whether the object experiences / suffer certain things. Diagnosing the levels is done to explain whether broccoli vegetables have calcium. It is hoped that with this system, ordinary people can solve certain problems both slightly complicated even without the help of experts in the field. As for experts, this system can be used as an experienced assistant. This developed application aims to make it easier to analyze the data. By using the Certainty Factor method, it will be easier to find out the diagnosis of calcium levels in broccoli. This method is the right method used in expert systems.