Room temperature pretreatment of pubescens by soaking in MgCl2 aqueous solution with different concentrations was studied. The solid residues were analyzed by Van Soest chemical titration, XRD, FT-IR, and XPS, while the filtrates were analyzed by GPC, HPLC, ESI-MS, and 2D HSQC. The soaking by 20 wt% MgCl2 solution resulted in relatively higher conversion rates of both hemicellulose (8.3 wt%) and lignin (5.3 wt%). Trace amounts of glucose and xylose were obtained in the filtrates, and the amounts were hardly varied by the addition of MgCl2. However, compared with the filtrate from the sample pretreated by water, different oligomers were detected in the filtrates, indicating that MgCl2 might be able to change the mechanism of dissolution conversion of pubescens, meanwhile, no LCC was found, indicating that MgCl2 pretreatment could promote the breakage of ether linkage between carbohydrate part and lignin part in LCCs. A new monophenol (LIG9) might be obtained from LIG1, which might be attributed to the promoted breakage of beta-O-4 in lignin by MgCl2 pretreatment. Compared with the sample pretreated by pure water, GPC analysis revealed that the proportion of larger compounds (M-n > 1700 Da) decreased while those of smaller compounds (M-n = 180-300, 300-800, and 800-1700 Da) all rose. (C) 2021 Elsevier Ltd. All rights reserved.