The electronic structure and thermoelectric property of Bi2S3 are investigated. The electron and hole effective mass of Bi2S3 is analyzed in detail, from which we find that the thermoelectric transportation varies in different directions in Bi2S3 crystal. Along ac plane the higher figure of merit (ZT) could be achieved. For n-type doped Bi2S3, the optimal doping concentration is found in the range of (1.0-5.0) x 10(19) cm(-3), in which the maximal ZT reaches 0.21 at 900 K, but along ZZ direction, the maximal ZT reaches 0.36. These findings provide a new understanding of thermoelectricity-dependent structure factors and improving ZT ways. The donor concentration N increases as T increases at one bar of pressure under a suitable chemical potential mu, but above this chemical potential mu, the donor concentration N keeps a constant. (C) 2013 Elsevier Ltd. All rights reserved.