There are several types of hidden export susides unregulated in the current WTO rules. We need a theoretical definition and a practical measurement of "hidden" export dubsides in order to regulate and eliminate them under the WTO rules. This paper classfied them systematically and specified which parts should be considered to be effective export subsides. In addition, regarding some of those measures, we caluculated the amount of export subsidy equivalents (ESEs) and examined possibilities dumping grain exports in major countries.