Grazing is the most common forms of human disturbance that caused the degradation of swamp vegetation. In the past decades, there were few studied on vegetation changes under the combined impact of grazing season and intensity. In this study, six plots were selected along grazing gradients based on the distance to settlement in a degraded swamp. The field survey were conducted from the beginning (1^st June) to the end (31^th October) across entirely growing season. Duncan's multiple comparison, univariate GLM analysis, species accumulation curves, PCA ordination and variance partitioning were employed to analyze the plant species richness and abundance, life form and plant community succession in the process of swamp vegetation degradation. The results showed that: A total of 46 vascular plant species across all seasons and plots were recorded. There were no significant difference between the spatial patterns of mean species richness within single sample across grazing gradients in June, September and October, and the mean species richness within single sample was highest in extreme and severe degradation stages and lowest in pristine swamp in July and August. The rates of species accumulation were highest in extreme and severe degradation stages along grazing gradients and highest in July and August along grazing season. The mean species richness within single sample had no significant correlation to grazing season, but had significant correlation to grazing pressure. The variance partitioning results indicated that the variation of species abundance with grazing intensity is much higher than that with grazing season, the variation explained by grazing intensity was 50.1%, explained by season and intersection were all negative. The total variation explained by grazing intensity and season was 47.6%. The mode of regressive succession tended to swamp→meadow and the transitory stage, namely swamp meadow, was atypical. The succession of constructive species followed the order of Carex meyerianaa→C. muliensis→C. brunea, but the direction of plant community succession remained stable. In terms of the composition of life form, the species richness in endlong decreased and that in bottom of lotus seed and stolon with great trample tolerance increased dramatically. In general, grazing season had no significant impact on species richness and abundance, but modified the patterns of species along grazing gradients and decreased the rates of species accumulation to some extent. As well as the grazing pressure changed the species richness, life form composition and the succession mode of swamp vegetation. But grazing may be served as one driving factors that determined the species richness patterns and succession of swamp vegetation.