Objective: This research explored the effect of high-fiber diet based on gut microbiota on chronic heart failure (HF) patients. Methods: Chronic HF patients, who had undergone a dietary survey indicating a daily dietary fiber intake of less than 15g/d were divided into the control and study groups (n = 50). In addition to conventional heart failure treatment, the study group received dietary guidance, while the control group did not receive any dietary guidance and maintained their usual low-fiber dietary habits. After one year intervention, the daily dietary fiber intake, abundance of gut microbiota, plasma trimethylamine N-oxide (TMAO), albumin (ALB), prealbumin (PA), transferrin (TF), C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-8 (IL-8), left ventricular ejection fraction (LVEF), left ventricular end-diastolic index (LVEDVI), and left ventricular end-systolic volume index (LVESVI), Barthel index (BI), and 6 min walking distance (6 MWD) were compared. Results: After intervention, in both groups, the daily dietary fiber intake increased, abundance of Firmicutes, Proteobacteria, Actinobacteria, Fusobacteria decreased and that of Bacteroides increased; the plasma TMAO decreased; serum ALB, PA, and TF levels increased; serum CRP, TNF-α, IL-6, and IL-8 levels decreased, and the change was greater in the study group; LVEF elevated, LVEDVI and LVESVI reduced, and the differences between both groups were not significant; BI and 6 MWD elevated, and the study group was higher than the control group. Conclusion: High-fiber diet positively regulates the composition of gut microbiota, nutritional status and microinflammatory level in chronic HF patients, thereby improving patients' quality of life.