The Lower Cretaceous strata containing abundant fossil plants and animals are well developed in Jiuquan Basin,northwest China.The fossils provide valuable materials to biostratigraphic researches and palaeoclimatic environment reconstruction.The present paper mainly focuses on the plant fossils collected from the Lower Cretaceous Zhonggou Formation of Jiuquan,Gansu Province,and is purposed on the palaeoclimatic and palaeoenvironmental studies during the Early Cretaceous of northwest Gansu,NW China.Based on the systematic field fossil collection,22 genera and 32 species of fossil plants were identified and described indoors.Of them,Equisetum tubers implies that significant seasonal variation had already formed in Jiuquan by the late Early Cretaceous.Tubers of Equisetum are described for the first time from the Lower Cretaceous Zhonggou Formation,Jiuquan Basin,Gansu Province,Northwest China.According to the similarity of the morphology and arrangement with extant Equisetum subgenus Equisetum,the present fossils are assigned to a new species of Equisetum.Furthermore,the cellular details of the tubers are clearly revealed for the first time.And the cellular morphology of extant Equisetum tubers can be compared to those of the fossil species.The occurrence of Equisetum would suggest a wet habitat,and the presence of tubers implies that burial occurred during the late fall or winter.