Abstract: In order to find an efficient way to enrich the silicon dioxide(SiO2) in straw, cornstalk was taken as an example. In this research, a new process consisting of steam-explosion, carding, sifting was employed to fractionize the cornstalk, followed by the quantitative analysis of silicon dioxide of the different parts of cornstalk. At the same time, SEM and XRD were introduced to analyze the transfer and the form change of SiO2. The results revealed that the content of SiO2 decreased with the sequence of leaf, stem and core. And the fractionation could accomplish the efficient separation of fiber cells from miscellaneous cells (epidermal cells, parenchyma cells etc) to realize the enrichment of SiO2. The XRD indicated that the amorphous form of SiO2 does not change after steam–explosion. The fractionization with steam explosion is beneficial to the enrichment of SiO2 in straw.