Diatoms from 87 sediment samples of the Core LV77-3-1 collected in southern part of Chukchi Sea were examined to reconstruct paleoenvironments of last millennia and correlate with sediment geochemistry data obtained from the same Core. Diatoms in Core Lv77-3-1 are represented by 161 species belonging to 61 genus (table 1). The largest number of species is characteristic of the genera Chaetoceros (15 taxa), Navicula (12), Thalassiosira (10), Coscinodiscus (8), Diploneis (8), Actinocyclus (7). Most species are marine, among which are 62 planktonic, benthic - 63 species. Considerable amount of freshwater (24 taxa) and extinct (12 taxa ) species are encountered but they are single. Analysis of diatoms on a detailed age model showed the periodicity of sedimentation in the zone of influence of the Pacific waters of the Chukchi Sea in the Late Holocene, which is characterized by alternation of relatively cold and warm epochs. The reconstructed changes do not fully reflect the global climate changes of the late Holocene. It is assumed that a possible cause of the discrepancy between ice conditions and global temperature changes is the inflow of warm Pacific waters through the Bering Strait, which increases the duration of the ice-free period.