This study assessed the effects of lactic acid bacteria (LAB), cellulase, cellulase-producing Bacillus pumilus and their combinations on the fermentation characteristics, chemical composition, bacterial community and in vitro digestibility of alfalfa silage.  A completely randomized design involving a 8 (silage additives)×3 or 2 (silage days) factorial arrangement of treatments was adopted in the present study.  The 8 silage additive treatments were: untreated alfalfa (control); two commercial additives (GFJ and Chikuso-1); an originally selected LAB (Lactobacillus plantarum a214) isolated from alfalfa silage; a cellulase-producing Bacillus (CB) isolated from fresh alfalfa; cellulase (C); and the combined additives (a214+C and a214+CB).  Silage fermentation characteristics, chemical composition and microorganism populations were analysed after 30, 60 and 65 days (60 days followed by exposure to air for five additional days).  In vitro digestibility was analysed for 30 and 60 days.  Compared with the other treatments, selected LAB a214, a214 combined with either C or CB, and Chikuso-1 had the decreased (P<0.001) pH and increased (P<0.001) lactic acid concentrations during the ensiling process, and there were no differences (P>0.05) among them.  Fiber degradation was not significant (P≥0.054) in any C or CB treatments.  The a214 treatment showed the highest (P=0.009) in vitro digestibility of dry matter (595.0 g kg^–1 DM) after ensiling and the highest abundance of Lactobacillus (69.42 and 79.81%, respectively) on days 60 and 65, compared to all of other treatments.  Overall, the silage quality of alfalfa was improved with the addition of a214, which indicates its potential as an alfalfa silage inoculant.