Yingen-Ejinaqi Basin is a Mesozoic-Cenozoic intermountain petroliferous basin in the Inner Mongolia, northern China, which was largely filled by the Cretaceous alluvial-fluvial-lacustrine clastic sediments interbedded with volcanic layers. Two sites of well-preserved petrified woods were discovered from the Lower Cretaceous Bayingebi Formation and Suhongtu Formation in the southeastern Basin. In this paper we described the taphonomic characteristics and morphological structures of petrified woods. And discussed the climatic environment when they buried in terms based on the palynologic datas. In addition, palynological samples are collected from the upper Bayingebi Formtion and lower Suhongtu Formtion. The palynological study suggests a late Early Cretaceous age, and also reflects a wet and warm climate in this area. According to the lithological characters, the first locality of the fossil woods are rapidly buried by intermittent floods, debris flows deposits. And the second ones are suddenly covered by pyroclastic deposits which possibly occurred at the late Early Cretaceous period on the basis of published dates.