Biomass is the sole carbon-containing renewable resource on Earth, and has high potential for the production of platform chemicals. Phenol, one of the most important platform chemicals, is generally derived from lignin conversion. In this study, the production of phenol from co-pyrolysis of cellulose and sodium borohydride at different mass ratios is investigated in detail. The results show that even a small amount of sodium borohydride (cellulose-sodium borohydride = 10:1) could effectively promote the conversion of cellulose to phenol through cellulose-derived levoglucosan intermediates. As the mass ratio of cellulose-sodium borohydride decreased, the relative content of phenol in the products significantly increased, and could be as high as 11.0% when the ratio of cellulose to sodium borohydride was 2:1. Glycosidic bonds in cellulose were considered to play an important role in its catalytic conversion. Furthermore, the resulting solid product could be used as a B-doping carbon material, which is desirable in various research fields. This study provided a novel method for the highly efficient utilization of cellulose.