Abstract: GIS Chinese query is to convert Chinese query sentence of GIS into SQL of spatial database through computer understanding.Aiming at the problem of complicated analysis of semanteme and uncertain table name of spatial attribute in current computer understanding of GIS Chinese query,the rule of building a casebase and the target comparability,structure comparability and individual comparability of case in reasoning machine are researched.The algorithm of CBR is designed and the conversion from GIS Chinese query sentence into spatial SQL is realized.The experiment results show that the strategy of CBR is correct and reasoning machine is feasible.