Investigated the thermoelectric properties (TE) of graphene nanoribbons (GNRs) by method of nonequilibrium Green's function approach and Landauer transport theory. The results show that TE of zigzag type GNRs decreases with its width increasing, TE of armchair edge GNRs are not only related to its width, but also with the band gap open or not, when it appears as a semiconductor, its thermoelectric properties are much larger than that of zigzag edge graphene nanoribbons.