Lignocellulose is the most abundant renewable resource on earth. However, owing to the tightly entangled structural characteristics, it is challenging to convert lignocellulose into bio-based products in the biorefinery process without pretreatment. Pretreatment can destroy the natural resistance structure of lignocellulosic biomass, which is conducive to its downstream enzymatic saccharification and fermentation process. Physical, chemical, and physicochemical pretreatments have been widely conducted for lignocellulosic biomass; several updated approaches and peculiar chemicals have also been proposed for these pretreatment methods in the recent years. Hence, this study comprehensively reviews the novel technologies and chemicals that were applied in the various pretreatments. In addition, the mechanisms, advantages, and disadvantages of the updated pretreatments are discussed to provide a reference for developing new pretreatment methods.