A novel antiretroviral protein Polygonatum cyrtonema lectin (PCL) belonging to the monocot mannose-binding lectin (MMBL) superfamily has been crystallized using hanging-drop vapor-diffusion method. The crystals diffract to 2.0 A resolution and belong to space group P2(1), with unit-cell parameters of a=39.308 A, b=48.317 A, c=112.221 A, and beta=90.12 degrees . Preliminary analysis indicates that the asymmetric unit contains four PCL molecules with a solvent content of about 45%. A set of X-ray data has been collected for the crystal structure determination.