Abstract: The forage nutrient content and fermentation quality of three C₄ forage grass species (Pennisetum purpureum, Sorghum bicolor×Sorghum sudanese and Zea mays) planted in Nanjing, Jiangsu Province, were analyzed after different wilting times, to investigate the patterns of change and formulate scientifically based guidelines for optimal wilting time during silage production. Six wilting treatments (CK, 1.5 h, 3.0 h, 4.5 h, 6.0 h and 7.5 h) were test, and samples from the different wilting treatments were analyzed for feed quality [dry matter content, in vitro dry matter digestibility (IVDMD), nonstructural carbohydrates (NSC), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents], and fermentation quality [pH, lactic acid (LA) and NH₃-N content] were analyzed. The dry matter content of all three C₄ forage grass species increased during wilting, the water content of S. bicolor×S. sudanese and Z. mays decreasing rapidly (P<0.05), while P. purpureum dried slowly and still retained a water content of 75.73% after wilting for 7.5 h. The NSC content decreased during the wilting period, but the water soluble carbohydrates (WSC) and starch which were the main components of NSC showed different time courses: the pattern of WSC change was like an inverted V, with an increase at the start of the wilting process, and then a decrease, while the starch content showed a steady decrease throughout the test period. The optimal wilting time for three C₄ grass species was 7.5 h for P. purpureum, 3.0 h for Z. mays, and 1.5 h for S. bicolor×S.sudanese.