Abstract: In order to observe the principles of grass carp osmotic dehydration, effects of temperature(5～30℃), time(2～24 h), NaCl(5%～15%) and maltodextrin concentration(0.6～1.2 g/g) and dosage of xanthan gum (0～0.004 g/g) on water loss, sugar gain and salt gain were researched during osmotic dehydration of grass carp sheets. The process of mass transfer was theoretically explained. Results show that high temperature and long time give raised water loss, sugar gain and salt gain. Increased NaCl concentration also resultes in higher water loss and salt gain, but has little influence on sugar gain. Increased maltodextrin concentration leads to salt gain decrease while sugar gain and water loss increase. With xanthan gum added, water loss, sugar gain and salt gain all decrease for viscosity of solution reduced.