A convenient and efficient procedure for isolation of rice HMW DNA bad been developed.Etiolated seedings were ground into the fine powder with a pestle and mortar under liquid nitrogen,then extracted with a protective medium,Filtrate was layered on discontinuous sucrose gradient,then the purified nuclei were embeded in agarose gel.After proteinase digestion,the HMW DNA was released. Pulsed-field gel electrophoresis showed that the sample size ranges from 200 kb to 3 Mb and in the majority of 2.2 Mb. Rice YAC library was constructed successfully, using these easily digestable DNA preparation.