Grasses exhibit variations in chemical composition and epiphytic microorganisms during daytime. These variations may influence the natural fermentation characteristics of silage. The objective of this study was to determine the effect of cutting times on chemical composition and epiphytic microorganisms of fresh napiergrass (
Pennisetum purpureumSch.) and of these effects on fermentation quality of unwilted silage on a sunny day. Primary growth of napiergrass was harvested in its vegetative stage at 0800 (AM), 1300 (M), and 1800 h (PM) on three sunny days. Napiergrass prepared at each cutting time was ensiled in laboratory silos in triplicate and sampled after 30 d to analyze the fermentation attributes and microbial counts. Bacterial community on fresh and post‐ensiled forage samples were determined by denaturing gradient gel electrophoresis, which were harvested on cutting Day 1. The results showed that 30‐d fermented napiergrass silages had good fermentation quality. Lactobacillus plantarumwas detected in all silages throughout the ensiling. The fermentation characteristics for silage made with PM‐cut napiergrass were better, with higher ( P< 0.05) dry matter, water‐soluble carbohydrates, and lactic acid concentrations and lower ( P< 0.05) NH3–N concentration, than those made with AM‐ and M‐cut forages. In conclusion, delayed‐cutting napiergrass on a sunny day was associated with good silage fermentation characteristics.