Cellulose nanocrystals (CNCs) were prepared and their properties were characterized in order to make the preparation process of nanocellulose more environmentally-friendly and ensure efficient utilization of forestry wastes. With pine wood powder as raw material and the help of acidic hydrogen peroxide and potassium hydroxide, lignin and hemicellulose were removed by chemical pretreatment, and the size was further reduced and the dispersibility of wood fiber was improved by mechanical treatment. Finally, CNCs were prepared successfully. FT-IR, DSC, SEM, TEM were used to analyze the composition, characterize the properties and observe the microscopic morphology of the samples. After delignification treatment, the carbonyl group (C=O) absorption peak at 1636 cm−1disappeared obviously; after the KOH de-hemicellulose treatment, the xylan carbonyl absorption peak at 1720 cm−1 disappeared. Besides, hollow cellulose, purified fiber and CNCs have similar shape of DSC curves, and the absorption peak value was at 125 ℃. Finally, after chemical pretreatment and mechanical shearing treatment, CNCs with uniform size and clear morphology are finally successfully prepared. And the radial size of CNCs is concentrated between 0 and 30 nm, and the axial dimension is mostly concentrated between 100 and 300 nm.