To investigate the effects of steam-flaked corn on flavor compounds in Simmental beef, 30 Simmental cattle with similar body weights were randomly assigned to three dietary groups. Group I received a diet containing 100% steam-flaked corn, Group II received and 50% steam-flaked corn, and the control group was fed a diet without steam-flaked corn. An amino acid analyzer combined with gas chromatography-mass spectrometry (GC-MS) was used to determine the contents of free amino acids, fatty acids, and volatile flavor compounds in beef, with the aim of clarifying the influence of different proportions of steam-flaked corn on beef flavor. The results showed that the total free amino acid contents in Group I and II were 10.81% and 8.53% higher, respectively, than that of the control group. The contents of umami and sweet amino acids increased significantly with increasing proportions of steam-flaked corn. Total fatty acid contents in the beef of the experimental groups were also significantly higher than those of the control group. Notably, the contents of monounsaturated fatty acids in Groups I and II were 81.82% and 44.03% higher, respectively, than those of the control group. Trans-linoleic acid (C18:2n6t) was detected only in Group I, with a content of 1.65 mg/100 g. Significant differences were also observed in volatile flavor compounds. The relative content of ketones was the highest in Group I (7.64%). Moreover, the contents of octanal (6.37%), dodecanal (2.55%), and nonanal (29.11%) in Group I were significantly higher than those in the other groups. Trans-2-undecenol, which imparts oily and sweet aromas, was detected exclusively in Group I at a content of 0.19%. Overall, increasing the proportion of steam-flaked corn in cattle diets significantly enhanced the contents of free amino acids, fatty acids, and volatile compounds in beef, thereby improving beef flavor (P<0.05). This study provides a reference for improving beef quality and production efficiency.