This study evaluated the effects of natamycin and Lactobacillus plantarum on the chemical composition, microbial community, and aerobic stability of Hybrid pennisetum at different temperatures. Different concentrations of natamycin (0.50 g L⁻¹, 1.00 g L⁻¹, and 1.50 mg L⁻¹) significantly (p > 0.05) reduced the growth of undesirable microorganisms. During the ensiling periods the pH, ammonia nitrogen (NH₃–N), acetic acid (AA), butyric acid (BA), aerobic bacteria (AB), and yeast were significantly (p > 0.05) reduced, while the lactic acid and lactic acid bacteria were significantly (p < 0.05) influenced in the SLP and SLNP groups as compared to the SP and SNP groups at high temperature (29–30 °C). During air exposure, water-soluble carbohydrate, ammonia nitrogen (NH₃–N), lactic acid (LA), and acetic acid (AA) were not influenced, while pH and aerobic bacteria were significantly (p < 0.05) enhanced after three days (72 hours) of air exposure, and lactic acid bacteria were significantly (p > 0.05) reduced at ambient temperature (9–10 °C). It is concluded that the addition of L. plantarum CICC 20765 alone and in combination with natamycin reduced the content of AA, pH, NH₃–N, BA, and undesirable microbial community, and enhanced the chemical composition, fermentation quality, and air exposure. Natamycin alone did not significantly enhance the organic acid profile but improved the air exposure. Furthermore, more effort is needed to evaluate the effects on silage preservation on a large scale and on animal performance.