Woody residence time is an important parameter that expresses the balance between mature forest recruitment/growth and mortality. Using field data collected from the literature, our group explored the global forest τw and investigated its influence on model simulations of aboveground biomass (AGB) at a global scale. We estimated the global 1 km τw using a random forest method by integrating the field based data, precipitation, Gross Primary Productivity, temperature, DEM and evapotranspiration as predictors. The estimated forest τwwas averaged 66.7 years globally with large spatial heterogeneity. The estimation of τw can help improve the model simulations and reduce the parameter’s uncertainty over the projection of future AGB in the current DGVM or Earth System Models.