Cerebral Palsy (CP) is one of the most complicated disabilities which is a permanent motor disorder causing mental and physical disabilities. Different reports published by different health organizations asked for researches on CP disability in order to improve diagnosis. Globally, there are different researches conducted to improve CP diagnosis, but most of those studies do not diagnose CP in children’s early ages, which limit the treatment impact. This paper report on a research conducted to develop an ontology-based approach to diagnose children with CP in early ages. In this paper, Ontology was used to represent CP domain. Then, a set of manually built rules have been optimized through a knowledge-based survey to be used in CP diagnosis. The proposed approach improves CP diagnosis and by consequence positively reflects physical therapy treatment. The proposed approach was evaluated by a real dataset consisted of 70 pre-diagnosed cases, where 84% correctly diagnosed
