Abstract: Biomass and carbon storage of Betula platyphylla natural secondary forests were studied based on 12 stands of 16 to 54 years old and forest inventory information in Mulan Forest Farm，Hebei Province of northern China. The biomass transition models in the form of power function were proposed. The average carbon density for B. platyphylla natural secondary forests was 187.076 0 t/hm2, of which 37.326 3, 144.306 0 and 5.443 5 t/hm2 were for tree, soil and ground layer, respectively. The existing total biomass and carbon storage of B. platyphylla natural secondary forests in Mulan Forest Farm were 1.376×106 and 2.962 ×106 t,respectively.