The invention relates to sulfomorpholine compounds, a preparation method thereof and a purpose thereof, and concretely relates to compounds of formula (I), or pharmaceutically acceptable salts thereof, free alkalis thereof, solvates thereof, esters thereof, prodrugs thereof, stereo isomers thereof, geometric isomers thereof and racemates thereof, wherein symbols in the formula (I) are shown in the specification. The invention also relates to a medicinal composition containing the compounds, a purpose of the compounds in the preparation of medicines for treating and/or preventing diseases or symptoms related with DPP-IV (dipeptidyl peptidase IV) hyperactivity or DPP-IV overexpression, and a method for treating relevant diseases with the compounds of the invention. The compounds of the invention can effectively inhibit the DPP-IV activity.