Based on determining the gross caloric values(GCV)of Kandelia obovata from different origins in north marginal region of natural mangrove wetlands, eastern China, the paper makes an analysis of the difference in caloric value among each organ and different intertidal positions of varied original K. obovata, and the changing law of caloric value with diameter class and latitude in natural forest. It came to conclusions that GCV among each organ of the K. obovata natural forests, trending to equal, was higher than that of plantation. High consistency in the order of caloric value of the various organs was emerged between natural and plantation K. obovata, which was leaf, flower, branch, stump, trunk, coarse root, fine root, medium root from the high to the low. Caloric value of K. obovata appeared upward trend with the extending outward of beach, and the trend of natural forests was more sensitive than that of plantations. In diameter class, the lager the diameter was, the higher the caloric value was(diameter ⅣⅢⅠⅡ). In addition, the change of diameter class made varying degrees of impact on each organ of K. obovata. Compared with latitudes in other region, the caloric value of natural K. obovata in north marginal region was lower, and also, the change of caloric value among various organs was not significant.