Objective： To investigate the quality control mechanism of glutinous rice flour during dynamic change of water in the process of semi-dry method. Method： Changes in apparent cracks image of grain surface and volume were evaluated. The damaged starch content， microscopic structure， hydration properties and pasting properties of glutinous rice flour with different hot air treatment time， soaking time and drying time were determined. Then hardness of glutinous rice grain and water changes trend during process were analyzed. Results： The longer the hot air pretreatment time， the more obvious the apparent crack of glutinous rice. The hardness of glutinous rice grain decreased during hot air treatment and soaking. Glutinous rice flour prepared by hot air treatment for 60 min， soaking for 35 min and drying for 30 min has high integrity of starch granules， good hydration properties and pasting properties. Glutinous rice （flour） contains most tightly bound water. Tightly bound water was lost during hot air and drying treatment while weakly bound water and free water content increased. The mobility of water increased during soaking and part of weakly bound water and free water transfer into tightly bound water. Conclusion： The "out-in-out" of water in rice grains and the dynamic transformation of different kinds of water in this process are the mechanism to reduce the hardness of rice grains and thus protect the integrity of starch granules， and finally obtain the glutinous rice flour with excellent quality.