Abstract: To improve the quality and shelf life of fungus chaff for silage, the microbiota and the effect of the addition of a fermented red elephant grass juice (FREGJ) were studied. Fungus chaff leftover from mushroom cultivation was incorporated with 2% FREGJ or distilled water (CK), vacuum packed in pouches with 5 replicates, and stored at room temperature for 1, 3, 7, 15, 30 and 60 days prior to testing. The 7 genera richly existed in the chaff-FREGJ mixture were dominated by Lactococcus genera, accounting for about 70% of the total microbial count, of which 75% were Leuconostoe mesenteroides. Quality of the fungus chaff was significantly improved by the addition of FREGJ with 15 d of fermentation (P < 0.05). However, after 30 d, undesirable microbes and harmful products significantly increased that could cause spoilage and shortened shelf life of the silage(P < 0.05).