The Lower Cretaceous Yixian Formation is the basal formation of the Jehol biota where the abundant and exceptionally wellpreserved fossils were discovered. However, deuteric late stage tectonic destructive disturbances and weathering effects have hampered field investigations on the Jehol biota's palaeogeographic and basin sedimentary characteristics, making it difficult to do detailed research. Our recent systematic field study of the depositional environment indicates that there were several lacustrine carbonate intervals in the four sedimentary beds of the Yixian Formation. We have systematically studied the distribution and the lithotypes of lacustrine carbonates both in the field and with laboratory analysis. Five main carbonate lithofacies have been differentiated in the lacustrine limestones, and they are further grouped into two main facies associations. Combining the relationship between the carbonates and other sedimentary beds, we find that the lacustrine carbonate sedimentary environment in the Yixian basin represents shortlived isolated ponds developed in very shallow depressions on the floodplain as well as brackish water in offshore lakes. Finally, we propose a lacustrine carbonate sedimentary facies model for the Yixian Formation.