Catalytic hydroconversion of C-18 fatty acids with different hydrogen donors (H-donors) was carried out in a fixed bed reactor to intensify the selectivity for preparing renewable diesel through advanced hydrodeoxygenation technology. Two types of H-donors, condensed aromatics and hydroxyl compounds, were investigated and found that the H-donors had little influence on the yields of C-15 and C-16 hydrocarbons but significant for C-17 and C-18 hydrocarbons. Condensed aromatics have a positive effect on the yields of C-17 and C-18 hydrocarbons. Alcohols significantly enhance the selectivity for C-18 hydrocarbon and suppress the selectivity for C-17 hydrocarbon. The yield of C-18 hydrocarbon is nearly doubled with 5 wt% ethanol. A multi-step mechanism is proposed to elucidate the phenomena. (C) 2014 Elsevier Ltd. All rights reserved.