The keyword searching mechanism is traditionally used for information retrieval from Web based systems. However, this system fails to meet the requirements in Web searching of the expert knowledge base based on the popular semantic systems. Semantic search of E-learning documents based on ontology is increasingly adopted in information retrieval systems. Ontology based system simplifies the task of finding correct information on the Web by building a search system based on the meaning of keyword instead of the keyword itself. The major function of the ontology based system is the development of specification of conceptualization which enhances the connection between the information present in the Web pages with that of the background knowledge.The semantic gap existing between the keyword found in documents and those in query can be matched suitably using Ontology based system. This paper provides a detailed account of the semantic search of E-learning documents using ontology based system by making comparison between various ontology systems. Based on this comparison, this survey attempts to identify the possible directions for future research.