Silage is traditionally and globally used as an important feed source for ruminants. The smell of silage affects not only feed intake of animals but also the milk flavor and quality. Stylo and rice straw were ensiled with or without a Lactobacillus plantarum strain (LP) for 30 days. Microbial communities were detected by Illumina HiSeq sequencing method and volatile chemicals for the smell features were also analyzed using a metabolomics approach. The addition of LP decreased (P < 0.05) weight loss, pH, ammonia-N content, butyric acid content and increased (P < 0.05) lactic acid content of the two silages. Totally, 117 volatile chemicals were identified in the two silages, including 45 esters, 16 terpenes, 12 aromatics, 10 alcohol, 9 alkanes, 8 heterocyclic compounds, 7 ketones, 4 aldehydes, 3 acids, 2 amines and 1 phenol. In stylo silage, 13 chemicals including 1-(2-hydroxy-5-methylphenyl)-ethanone, 1-hexanol, tetradecanoic acid, ethyl ester, vinyl trans-cinnamate, 3-methyl-1-butanol, butyl caprate, butyl benzoate, N-methyl-formamide, 3-phenylpropanol, phenylethyl alcohol, butanoic acid, butyl ester, propanoic acid, ethyl ester and 3-(1-methylethyl)-oxetane were downregulated by LP. In rice straw silage, 6 volatile chemicals including propanoic acid, butyl ester, propanoic acid, hexyl ester, 1-(2-hydroxy-5-methylphenyl)-ethanone, (4-methoxyphenyl)-hydrazine, 4-ethyl-2-methoxy-phenol and 1-(2,4-dihydroxyphenyl)-ethanone were downregulated by LP. Almost all these chemicals were positively correlated (P < 0.05) with the relative abundance of Kosakonia, Enterobacter, Lachnoclostridium and Nigrospora, and were negatively correlated (P < 0.05) with the relative abundance of Lactobacillus, Methylobacterium, Sphingomonas. In conclusion, microbiota has influence on volatile metabolites of silages. Lactic acid bacteria inoculants could alter the smell by changing microbial communities of the silage. This study provides a new insight into intrinsic characteristics related to smell of silages and a potential way to change.