Abstract: A mild hydrogenation of simulated bio-oil was carried out in a fixed-bed reactor. Based on the experimental results, 300℃/4 MPa was chosen as an optimum condition for the mild hydrogenation, the simulated bio-oil was nearly completely converted. Besides, the liquid product selectivity achieved 85.0% and its (H/C)_eff was significantly promoted from 1.266 to 1.554. The liquid composition was greatly improved and a notable decrease of phenols and acids contents was observed. In this case, the product activity was significantly enhanced and then the subsequent catalytic cracking was favored.