The results obtained by using an Oxygen-bomb calorimeter showed that the caloric value (energy state) of soil humic acid under different conditions of fertilization decreased in the following order: compost > straw > chemical fertilizer > no fertilizer > fallow. The energy state of fixed position experiment of ten years was lower than that of four years.The results of thermal analysis showed that soil humic acid under different conditions of fertilization had a similar peak of heat effect and peak of weight loss. The treatment of organic fertilizer applied tended to low in both the enthalpy change value of 460℃ exothermic peak of DTA and activation energy of weight loss peak of DTG. The 340℃ exothermic peak of DTA of humic acid in the fixed position experiment of ten years was not more obvious and the enthalpy change value of 460℃ exothermic peak was higher than those of four years. The activation energy of weight loss peak of DTG .than in the fouz-years fixed was higher in the ten-year fixed position experiment positron experiment.