In this study, a deep eutectic solvent (DES) pretreatment using choline chloride (ChCl)/lactic acid (LA), betaine (BE)/LA, and potassium carbonate (PC)/glycerol (GLY) was used to prepare lignocellulose nanofibrils (LCNF). An increase in the reaction temperature (100, 120, and 130 °C) and time (6, 12, and 24 h) caused a decrease in the content of lignin and hemicellulose in lignocellulose (Pinus densiflora S. et Z.). Lignocellulose nanofibrils (LCNFs) were prepared from the DES-treated products using a high-pressure homogenizer. As the lignin content of the DES-treated products decreased, the defibrillation efficiency of the LCNFs improved, resulting in a smaller diameter, longer filtration time, larger specific surface area, higher water retention value, and higher viscosity. DES pretreatment using ChCl/LA was more effective for delignification and improvement of defibrillation efficiency than pretreatment using BE/LA and PC/GLY. A decrease in the lignin content caused an increase in the crystallinity index and crystallite size. The significant delignification due to the ChCl/LA treatment can be attributed to the improved tensile properties of the LCNF nanosheets. [ABSTRACT FROM AUTHOR]