Biostratigraphy,magnetostratigraphy and other evidences from Well SK1suggest that the Cretaceous/Paleogene(K/Pg)boundary lies in the upper part of the Member 2of the Mingshui Formation in the Songliao Basin, Northeast China.In order to determine the inferred position of the K/Pg boundary,the sporepollen fossils of the Mingshui Formation from Well LD17,which is located in west slope of the Songliao Basin,are analyzed in this study. Three zonations are identified in ascending order:Taxodiaceaepollenites-Wodehouseia-Aquilapollenites,Schizaeoisporites-Pinuspollenites-Callistopollenites and Pinuspollenites-Ulmipollenites-Tricolpollenites zones.It is deduced that the age of the Zone 1and Zone 2is Maastrichtian,while Zone 3might be of the Early Paleocene.Hence,it is likely that the K/Pg boundary is within the bottom of the Zone 3,i.e.the middle part of the Mingshui Formation. The Member 1of the Mingshui Formation is rich in sporepollen fossils,which is quantitatively analysed.The result indicates a subhumid subtropical paleoclimate condition,with vegetation of theropencedrymion and shrub.A cooling and wetting event might happen in the middle part of the Member 1of the Mingshui Formation(early Maastrichtian), consistent with the contemporaneous global cooling.