A pretreatment step for lignocelluloses is responsible to alter the complex structure which allows enhancing enzymatic accessibility and bioconversion of the materials. However, there is a gap on the methods to characterize physical evolutions of the material throughout its pretreatment. The aim of this study is to evaluate the physical changes in rice straw (RS) pretreated with alkaline followed by grinding to produce biopowders. A hydro-textural approach was applied to evaluate the physical changes of RS pretreated by impregnation and soaking in NaOH. The results indicated that the volume deformation increased by 110%, while the energy consumption decreased by 11.3% compared to unpretreated RS. Moreover, the cellulose content and glucose were 66.8 and 212 mg/g RS obtained by RS soaking. The alkaline-mechanical pretreatment was shown as an effective process to provide high glucose readily converted to bioethanol. Additionally, the hydro-textural approach can be considered an alternative method for biomass structural characterization.