Abstract: The Casuarina equisetifolia litter decomposition experiment site locates at Huian county in Fujian province, south of China. Caloric value were tested by oxygenic bomb caloric-meter. The aim was to expose the law of gross caloric value, ash free caloric value and ash content of litter during decomposition. The result showed the dynamic of the gross caloric value, ash free caloric value and ash content of Casuarina equisetifolia litter during decomposing. The decomposation lasted for three months with the caloric 21.40 kJ·g-1, to which decreased from the beginning gross caloric 21.67 kJ·g-1. At the tenth month, the gross caloric value was decreased to rock bottom, 20.48 kJ·g-1, with the range 1.19 kJ·g-1 to the begin value. After ten months of decomposation, the gross caloric value began to increase, then gross caloric value increased to 20.83 kJ·g-1 at the twelfth month, while with average decreasing ratio 0.07 kJ·g-1 per month; As to ash free caloric value, which the beginning ash free caloric 22.78 kJ·g-1, decreased to nadir, 21.89 kJ·g-1 at the ninth month, with the range 0.89 kJ·g-1 to the begin value. Then it increased faster than gross caloric did, up to 22.41 kJ·g-1 at the twelfth month. While it had average decreasing ratio 0.03 kJ·g-1 per month; The ash content, which had the contrary tendency to caloric, increased with time go by. But as the gross caloric, they all reflected the law of litter decomposition. It increased slowly from 4.88% to 4.90% in the beginning three months, then increased sharply. At the twelfth month, the ash content was up to 7.09%,and with average increasing ratio 0.184 point of percentage per month, in twelve months. While both caloric and ash content related obviously with temperature and soil temperature, especial the air temperature, so temperature was an important factor effecting the litter decomposition.