In order to enable rapid disposal and proper preservation of discarded vegetable for waste valorization, ensiling was employed to preserve cauliflower leaves for 30 days at different temperatures (20 ~ 45 °C) with and without the addition of Lactobacillus plantarum L8. The L. plantarum inoculant reduced dry matter (DM) loss and enhanced the preservation of protein and soluble carbohydrate while decreasing pH and ammonia nitrogen content. The silages at 35 °C exhibited the best fermentation profile characterized by the highest lactic acid content (185 g·kg DM) and the lowest pH (4.08) and ammonia nitrogen content (37.6 g·kg total nitrogen) with L. plantarum inoculation. The presence of exogenous L. plantarum improved the silage fermentation, enriched Lactobacillus and Weissella, and reduced the microbial richness/diversity, resulting in efficient lactic acid fermentation, especially at 30 and 35 °C. Moreover, the microbial community dynamics was correlated with the chemical compositions and fermentation metabolites in silages.