The object of this work was to evaluate the effect of loading coefficient on steam explosion process and efficacy of corn stalk. Loading coefficient's relation with loading pattern and material property was first revealed, then its effect on transfer process and pretreatment efficacy of steam explosion was assessed by established models and enzymatic hydrolysis tests, respectively, in order to propose its optimization strategy for improving the process economy. Results showed that loading coefficient was mainly determined by loading pattern, moisture content and chip size. Both compact loading pattern and low moisture content improved the energy efficiency of steam explosion pretreatment and overall sugar yield of pretreated materials, indicating that they are desirable to improve the process economy. Pretreatment of small chip size showed opposite effects in pretreatment energy efficiency and enzymatic hydrolysis performance, thus its optimization should be balanced in investigated aspects according to further techno-economical evaluation. (C) 2014 Elsevier Ltd. All rights reserved.