Abstract: The expansion of semantic levels of concept is analyzed，the relationship between father and son concept in concept tree is translated by the similarity of words.Two methods，which are based on computing retrieval concept weight，and one method，which is based on computing text concept weight based on retrieval concept，are proposed.These methods are used in Chinese text retrieval.So，two text retrieval models are constructed based on concept tree expansion.Experiments show that the precision of the two retrieval models can be in line with keyword retrieval model，but the recall rate is improved greatly.