Abstract: The narometer magnesium oxide (MgO) was used as catalysis for the preparation of lignin-phenol-formaldehyde (MLPF) resin. MgO was added in the initial stage of resin reaction. The molecular structure and thermal behavior of the curing reaction of MLPF resin were characterized by Fourier transform infrare spectroscopic (FT-IR), 13C nuclear magnetic resonance (13C NMR) and different scanning calorimetry (DSC), respectively. A comparisons to phenol-formaldehyde (PF) resin and lignin-phenol-formaldehyde(LPF) resin without adding MgO were also carried out to investigate the effects of Mg2+ on the structure and curing characteristics of MLPF resin. The research results indicated that Mg2+ could promote the formation of hydroxymethyl group, increase the amounts of methylene, restrict the formation of ether bond bridge during MLPF resin synthesis, and lead to the higher structure condensation degree of MLPF resin than that of LPF resin. MgO seemed to make MLPF resin cure faster and decrease its curing reaction temperature.