By developing ontology we can share the common understanding of the structure of information among users or software agents. Different websites may contain variety of details about diagnosing the diseases of date palm. Ontology where fundamental in our system, where contain enough information about the diseases, symptoms etc. Information retrieval is done through the language queries will be explained later. Through ontology all these information can be aggregated and can be published. The users and agents can use this aggregated information to answer user queries or as input data to other applications. The developed ontology can be reused in the future for other purposes. To build a larger ontology, the existing ontologies describing portions of the large domain can be integrated. We can conclude that of AgriDPalmOnto is to speed of response and accuracy in information and extract new information resulting from relations in it.