Based on the location observation data of the tropical seasonal rain forest in Xishuangbanna, the subtropical evergreen broadleaved forest in Dinghu Mountain, the moist evergreen broad-leaved forest in Ailao Mountain and the broad-leaved Korean pine forest in Changbai Mountain, this paper analyzed and compared the spatial distribution patterns of carbon content and carbon density in four forest ecosystems. The results showed that the carbon contents of vegetation in Ailao Mountain and Changbai Mountain were higher than those in Xishuangbanna and Dinghu Mountain, the carbon contents of different layers in four forest ecosystems were in the order of tree>shrub>herbage. The total carbon density was 250.768 t/hm2 in Xishuangbanna, 248.709 t/hm2 in Dinghushan Mountain, 530.141 t/hm2 in Ailao Mountain and 254.671 t/hm2 in Changbai Mountain. The carbon densities of vegetation in Xishuangbanna, Dinghu Mountain and Changbai Mountain were higher than those of soil, but it was opposite in Ailao Mountain.