The research on biomass conversion technology has attracted great attention of the world along with the shortage of fossil energy resources. But the effect and efficiency of the pretreatment technique now used in biomass conversion are not so perfect. Using new steam explosion technique as a pretreatment process of biomass conversion has been reported rarely. The mechanism of steam explosion and its application effect in biomass conversion and utilization were introduced and analyzed respectively in this paper. The result showed that the semi-cellulose of steam exploded corn stalk degraded greatly to 7.57% from 25.4%, and a little cellulose and lignin degraded in this process. The saccharification rate of steam exploded green reserved corn stalk was 33.4% under the condition 2.0Mpa, 120s. It’s 1.33 times higher than the unexploded. According to the result of experimentation, the steam explosion technique should be a good pretreatment method for biomass conversion.