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Forest litter accumulation and decomposition contribute to the nutrient pool and are critical ecological processes in the ecosystem. The Casuarina equisetifolia L.coastal protection forest（CCPF） in Hainan Island was the focus of this study, and a total of 71 temporary sample plots were set up to investigate and analyze the stand structure and litter accumulation in CCPF by means of typical survey sampling, in order to explore the amount and impact factors of litter accumulation on C. equisetifolia. The results showed that six factors affect litter accumulation of CCPF, including the average diameter at breast height（DBH）, basal area, density, canopy density, herb coverage, and pH value; litter accumulation was significantly positively correlated with the average DBH, basal area, and canopy density（P<0.01）, highly negatively correlated with herb coverage（P<0.01）, positively correlated with density, and negatively correlated with pH value. The impact factors and related properties of semi-decomposed litter mass were consistent with those of litter accumulation, but they were negatively correlated with pH value（P<0.05）. There was no significant difference in litter accumulation in different semiarid and wet climate regions of Hainan Island（P>0.05）. In addition, the six impact factors can be divided into direct and indirect factors, and into main and non-main factors according to their different impact modes and degrees on the litter accumulation. Among them, average DBH, basal area, and density were considered direct impact factors, whereas canopy density, herb coverage, and pH value were indirect impact factors. The basal area and herb coverage were the main impact factors, among which herb coverage was an important indicator of litter accumulation. The level of litter accumulation of CCPF was high, with an average of 2.735 kg·m-2 and a maximum value of 10.090 kg·m-2. The average litter thickness was 3.629 cm, and the maximum thickness was 8 cm. In litter accumulation, the semi-decomposed litter mass accounted for 72.249%. Therefore, a large amount of litter accumulation is not only an important nutrient source for C. equisetifolia, but also one of the barriers to the regeneration of undergrowth plants. [ABSTRACT FROM AUTHOR]