Xylan, galactoglucomannan, arabinogalactan and hemicelluloses with different molecular weights were prepared from wood and then used as wet-end additives and surface sizing agents in papermaking. The results showed that xylan, galactoglucomannan and arabinogalactan all had obvious paper-strengthening effect. As wet-end additives, galactoglucomannan had the best effects, followed by xylan and then arabinogalactan. As surface sizing agents coordinating with starch, xylan showed the best sizing effect (paper-strengthening effect and water resistance), followed by galactoglucomannan. The effects were both greater than that of starch alone. Furthermore, hemicelluloses with higher molecular weights had more significant effects. The results could provide some reference for the use of hemicelluloses in nature and papermaking waste liquor to improve paper physical strength. Although hemicelluloses in APMP (alkaline peroxide mechanical pulp) waste liquor was degraded to a certain degree, it also showed good paper-strengthening effects. Starch as an important papermaking additives comes mainly from food. The hemicelluloses, especially in the high-yield-pulp waste-liquor, can replace starch in papermaking to some extent, which might be beneficial from economic, energy and food standpoints.Highlights► The structure of hemicelluloses influences their paper-strengthening effects. ► Hemicelluloses mixed with paste starch as surface sizing agent showed obvious effect. ► The effects of APMP hemicellulose differ not widely from wood hemicellulose. ► Hemicellulose can be used instead of starch partly. ► Use of HYP-waste-liquor hemicellulose responds to economic, energy, food concerns.