Abstract: This study aimed to assess the effect of outdoor storage time on quality of corn stover raw material and to evaluate the effect of storage time （T） and lactic acid bacteria （LAB） and cellulase （CE） addition on fermentation quality of corn stover silage. Tow storage time was set in this study （TI： silaging immediately after the harvest of corn cob; T2： silaging after 5-month outdoor storage）; there were four treatments for each storage time and there were three repeats for each treatment; the water content of the raw materials was initially adjusted to 60%, and then the materials were added with 2.0 g/t of LAB, 2.0 g/t of CE, and 2.0 g/t of LAB＋2.0 g/t of CE （LAB＋CE） to prepare silage, respectively; the CK treatment received no additives. The results revealed that compared to the fresh corn stover, the content of water soluble carbohydrate （WSC） and crude protein （CP） as well as buffer capacity （BC） of the corn stover stored for 5 months outdoor was significantly reduced （P〈0.05）, and the content of neutral detergent fiber （NDF）, acid detergent fibre （ADF） and acid detergent lignin （ADL） was significantly increased （P〈 0.05）; compared to the silage prepared with corn stover stored for 5 months, the silage prepared with fresh corn stover had lower pH value and acetic acid （AA） content （P〈0.05） and had higher lactic acid （LA） content, lactic acid/acetic acid （LA/AA） and ammonia nitrogen/total nitrogen （AN/TN,P〈0.05）; the addition of LAB significantly reduced the pH value and AA content （P〈 0.05） and significantly increased the AA content and LA/AA （P〈0.05）; the addition of CE significantly reduced the pH value （P〈0.05） and significantly increased the LA content and LA/AA （P〈0.05）; T and LAB addition had significant effect on all of the indexes associated with fermentation quality （P〈0.05）; CE addition had significant effect on pH value, LA and AA content as well as LA/AA （P〈0.05）; T and LAB addition had significant interactive effect on pH value, AA content and LA/AA （P〈0.05）. The combined data suggest that the silage should be immediately prepared after the harvest of corn cob; the addition of LAB and CE effectively improves the fermentation quality of corn stover silage, and LAB exhibits a better performance than CE.