Based on located observation and chemical analyses in the Casuarina equisetifolia plantation of 15 years, the geochemical cycling in the ecosystem was studied. The results showed that the total amount of nutrient elements in precipitation was 49．285 kg·hm-2·a-1and that in runoff was 15．507　kg·hm-2·a-1， so the net accumulation of them was 33．778 kg·hm-2·a-1 This revealed that the ecosystem was at its progressive phase. Compared with the biological cycling, the net accumulation of the geochemical cyching was less than 75．6%， so the biological cycling was operating faster and more intensively than the geochemical cyching. 