Abstract: In order to determine the right curing technology and improving the quality and usability of burley tobacco, the major physical and chemical changes of burley tobacco during curing were studied from 1999 to 2001 in Enshi, Hubei province.The results showed that 1)the curing process were divided into yellowing, browning and stemdrying stages, the mean relative humidity in the barn in a day during the three curing stages should be held at 70%-80%, 65%-75% and 50%-55%, respectively;2)the water loss rate was gradually reduced with the lapse of curing time, and the relative water loss ratio of tobacco plants during yellowing, browning and stem-drying stages was 60%-65%, about 20% and below 20%, respectively;3)total N content of tobacco leaves wasn't clearly varied and nicotine content was changed in a narrow range during curing, reducing sugar was sharply decreased at early stage and wasn't obviously changed at later stage of the curing process.