This study aimed to investigate the microorganism profile, fermentation quality and rumen digestibility in vitro of maize-stalk silage at different maturity stages. Maize-stalk samples were harvested at the stages milk-ripe, dough, fully ripe, and fully ripe exposed to air for 3 or 10 days. Silage pH, ammonia-N and chemical composition were measured. Thirteen representative lactic acid bacteria (LAB) strains isolated from the raw materials were categorised into five profile clusters: Leuconostoc citreum (23.1%), Weissella paramesenteroides (15.4%), Lactococcus garvieae (23.1%), Enterococcus faecalis (7.7%), and Lactobacillus paraplantarum (30.8%). The total LAB numbers in silages with raw materials reaped at the stages milk-ripe, dough, fully ripe, and fully ripe exposed to air for 3 or 10 days, respectively, were approximately 8, 6, 10, 3.5 and 10 log CFU g^–1. The dominant LAB types of maize-stalk silage at different stages were all different. The epiphytic pathogens Escherichia coli, aerobic bacteria, filamentous fungi and Saccharomycetes were found in silages of all stages. There were significant differences (P < 0.001) in crude protein, ether extract, dry matter, acid detergent fibre and organic matter of silage at different stages; however, no significant difference (P > 0.05) was observed in dry matter digestibility after 24 h of fermentation in vitro, with NH₃-N varying from 0.7 ± 0.1 to 1.7 ± 0.3 mg L^–1.