Commercial phenol-formaldehyde (PF) adhesive was gradually substituted by increasing amount of the phenol-rich fraction (PRF) of crude bio-oil up to 40wt%. The effect of substitution level of the PRF on the chemical, curing, morphological scanning electronic microscope(SEM), and bonding characteristics of the PF adhesive was determined. The tensile-shear strength of single lap-joint wood specimens bonded with the modified PF adhesives was investigated under indoor and outdoor exposure conditions. The chemical composition of the PRF was investigated using some chromatographic and spectroscopic techniques. Further structural analysis of PRF-modified PF adhesives was determined using Fourier transform infrared spectroscopy(FTIR). The PRF resol had a similar molecular structure to commercial pure phenol resol adhesive. The PRF could be partially substitute for the petroleum-based phenol in commercial PF adhesives with inexpensive phenols derived from lignocellulosic wastes.