From 1996 to 2006, there is a little increasing on the amount of export of cereal product in China overall, but the amount of export fluctuates greatly during years. By the analysis of constant market share model, we conclude that the most important factor of cereal export fluctuation in China is competitiveness of export. Therefore, in order to keep the steady development of cereal export, it is necessary to improve the technical share of the cereal product and to improve its competitiveness.