The well known Cretaceous seaway in North America was recognized in the middle of the last century and the Palaeogene seaway in East China was proposed by the author recently.The two seaways located on the opposite sides of North Pacific Ocean may be not a coincidence,and a comparative study was made in this paper.The results show that the two seaways inundated basins share several similarities particularly in basin origin,filling processes and reservoir facies. It is suggested that reservoir facies of estuarine sandstone and shelf bar sandstone related to sea level fluctuation,which are well developed in the Cretaceous seaway covered basins in North America might have been also developed here in Palaeogene seaway inundated basins in East China.Therefore it is worth paying more attention to finding these new reservoir facies on this side of the Pacific ocean.Evidences of sedimentology and ichnology indicate that good prospects are likely. The well known Cretaceous seaway in North America was recognized in the middle of the last century and the Palaeogene seaway in East China was proposed by the author recently. Two waterways located on the opposite sides of North Pacific Ocean may be not coincidence, and a comparative study was made in this paper. The results show that the two seaways inundated basins share several similarities particularly in basin origin, filling processes and reservoir facies. It is suggested that reservoir facies of estuarine sandstone and shelf bar sandstone related to sea level fluctuation , which are well developed in the Cretaceous seaway covered basins in North America might have been also developed here in Palaeogene seaway inundated basins in East China. Wherefore it is worth paying more attention to finding these new reservoir facies on this side of the Pacific ocean. Evidences of sedimentology and ichnology indicate that good prospects are likely.