Hemicellulose has a wide range of applications, including that as an emulsifier for the food industry and raw material for the synthesis of bioethanol/biochemicals and biodegradable films. Hemicellulose is usually present as a spent liquor, such as the prehydrolysis liquor of the prehydrolysis kraft dissolving pulp production process and the alkali extraction liquor of the cold caustic extraction of pulp fibers. Due to its dilute nature, hemicellulose needs to be dried for practical utilization, and this is challenging. In this study, cellulose and hemicellulose in a bleached bamboo kraft pulp were separated using an alkali extraction process. Hemicellulose obtained from the extraction liquor was dried by an ammonium carbonate-assisted drying process. The effects of drying time and drying temperature were determined. Structure of the hemicellulose obtained by the ammonium carbonate-assisted drying process was similar to that of original hemicellulose, as revealed by detailed Fourier transform infrared and X-ray diffraction analyses. The novel drying method was more energy efficient and required a shorter drying time than the conventional freeze drying method, and the excellent solubility in alkaline solutions favored the chemical modification of hemicellulose. The dried hemicellulose can be used as a renewable raw material for the preparation of hydrogels and other substances such as bioethanol/biochemicals and biodegradable films.