We studied the formation of heartwood in Erythrophleum fordii Oliv., an endangered rosewood species, by cross-section analysis on 52 stumps aged 28–57 years and arbitrarily sampled from natural forests in South China. Width and area of heartwood were positively correlated with age and xylem width(XW), and were independent of annual radial growth. The proportions of heartwood and sapwood areas were equal at about 40 years. The heartwood formation process was simulated by linear regression of age and XW. We studied the formation of heartwood in Erythrophleum fordii Oliv., An endangered rosewood species, by cross-section analysis on 52 stumps aged 28-57 years and arbitrarily sampled from natural forests in South China. Width and area of ​​heartwood were positively correlated with age and xylem width (XW), and were independent of annual radial growth. The proportions of heartwood and sapwood areas were equal at about 40 years. The heartwood formation process was simulated by linear regression of age and XW.