1． College of Geo- Exploration Science and Technology，Jilin University，Changchun 130026，China; 2． Northeast Electric Power Design Institute，China Power Engineering Consulting Group， Changchun 130021，China

Ｒeverse Time Migration (ＲTM) is a high precision imaging method of seismic wavefield at present， but low- frequency noises severely affect its imaging results． Thus one of most important aspect of ＲTM is to se- lect the proper noise suppression method． The wavefield characteristics of the Poynting vector are analyzed and the upgoing，downgoing，leftgoing and rightgoing waves are decomposed using the Poynting vector of the acous- tic wave equation． The normalized wavefield decomposition cross- correlation imaging condition is used to sup- press low- frequency noises in ＲTM and improve the imaging precision． Numerical experiments using the Mamousi velocity model are performed and the results demonstrate that the upgoing，downgoing，leftgoing and rightgoing waves are well decomposed using the Poynting vector． Compared with the normalized cross- correlation imaging and Laplacian filtering method， the results indicate that the low- frequency noises are well suppressed by using the normalized wavefield decomposition cross- correlation imaging condition．