Abstract: Fifteen surface sediment sample from Arctic Ocean were analyzed using X-ray diffraction (XRD) technique to determine their clay mineral compositions as well as illite crystallinity index. The distribution pattern of clay minerals and the illite crystallinity index (Ns) of the study area are shown, and the sources of clay minerals, sedimentary environments and hydrodynamic conditions are discussed. The clay minerals are dominated by illite (33%), followed by illite/smectite (25%), chlorite (23%), kaolinite (15%), and smectite (4%). The illite crystallinity index of the study area is low (mostly between 1~2). It is suggested that the crystallinity index of illite is a good indicator for the source of clay minerals. The Chukchi Sea has relatively weak hydrodynamic condition with stable sedimentary environment, while Bering Sea has stronger hydrodynamic condition with erosional sedimentary environment. The sources of the sediments in the Arctic Ocean are mainly from river input, and authigenic clay mineral and ice-rafted materials also make part contributions.