Abstract:This paper deals with the biomass of the ravine tropicalrain forest at an elevation of 720m(N 22°4/-16/; E 100 ° 32/-44/) in Xishuangbanna. The result showsthat the total biomass is 335.036 t.hm-2 ,of which the tree- layer is 321.185 t.hm-2(95.86%), shrub layer 2.664 t.hm-2(0.80%), herb layer 1.635 t.hm-2/(0.49%), liana 4.078t.hm-2(1.22%), epiphyte 0.092% t.hm-2(0.03% ),litter 5.382 t.hm-2(l1.61%).