The purpose were design and develop software engineering web based expert system to diagnose depression on human to get solution and information easily and rapidly. This research used Certainty Factor of analyzed method base of user answer for question in this expert system. Output were showed as user condition related depression and were completed with disease explanation and medical solution which showed in website with PHP programming of MySQL database. The conclution in this research were PHP programming and MySQL database evidently could be implemented in expert system engineering to diagnose depression. Certainty Factor method evidently could commit searching depression symtomp easily and rapidly. Online system could support user to get information about kind of disease, symptom, and medical solution for depression.