The main objective of this study was to estimate the above-ground biomass in the Miombo forest of the Haut Katanga ecological system in the Democratic Republic of Congo; the case of the “Notre Dame” monastery’s forest of Kiswishi. So, the allometric method was used that consist in the proportionality relation between the relative growth and the mensurations. The evaluated parameters were the terrier area, the above ground biomass according to the Brown’s model (1997) and the estimation of the carbon dioxide emissions for the treeless superficies. On the two selected plots with the medium density of 562 trees per hectare, it was estimated, according to the diameter at the chest height, the above ground biomass of 168.8 metric ton per hectare; the terrier area of 18.86 m2/ha and 618.95 metric ton per hectare of carbon dioxide that would be sent out in the atmosphere if all trees of the ground were cut down and burnt. In conclusion, the Miombo forest of Kiswishi accuse low biomass seeing that it is mainly represented by trees with à diameter at the chest height less than 30 cm.