The effects of liquid hot water combined with 1, 4-butanediol (LHW-BDO) on the chemical composition and structure of moso bamboo were investigated. The structure changes of moso bamboo fibers were characterized by infrared spectroscopy, X-ray diffraction, and electronic scanning electron microscopy. The results showed that the delignification rates of 1, 4-butanediol (BDO) and LHW-BDO pretreatment methods were at the same level (91.42-93.08%). However, compared with BDO pretreatment, the cellulose content in solid residue after LHW-BDO pretreatment was increased by 17.06% with a recovery rate of 75.68%, while the hemicellulose removal rate increased by 115.33% and reached 50.34%. After LHW-BDO pretreatment, the intramolecular hydrogen bonds, intermolecular hydrogen bonds, methylene bonds, and aromatic ether bonds of the fibers were broken, which contributed to the depolymerization and separation of cellulose, hemicellulose, and lignin molecules. However, LHW-BDO pretreatment does not destroy the beta-glycoside bond which links the glucose molecule inside the fiber molecule, which was also beneficial to the separation of cellulose. In addition, the amorphous zone of bamboo fibers was destroyed by the above treatments, and the fiber structure of bamboo samples mostly exists in crystalline form. The crystallinity of bamboo pretreated with LHW-BDO was increased by 32.15%. It can be found by scanning electron microscopy that the surface of the pretreated bamboo samples showed uniformly distributed bubbly protuberance.