Abstract: The Sunjiawan Formation in Pingzhuang area, Inner Mongolia, a set of epicontinental clastic assemblage occurring as interbeded conglomerate and sandstone, is divided into two rock members based on the lithologic association characteristics. The first member is polymictic conglomerate with purple greywacke in partial. The second is the assemblage of tuffaceous siltstone, sandstone, conglomerate and conglomeratic gritstone. The Sunjiawan Formation is rich in palynofossils, consisting of fern spores and gymnospermae pollen, without angiospermae pollen. According to the age of Aptian-Albian sporo-pollen assemblage, it is inferred that the Sunjiawan Formation was formed in the late period of Early Cretaceous.