Biomass production and productivity of a Sassafras t.zumu forest were measured by models of allometry method in Jianyang Shufang Forest Farm of Fujiang Province. The forest was naturally regenerated by dominant S. tzumu after final cutting of Cunninghamia lancenlata plantation at about 20 year's succession with density of S. tzumu trees ca. 480 individuals per ha. The results showed that mean total biomass production and mean annual productivity of S. tzumu trees were 58 693 kg hm-2 and 4 259 kg hm-2, respectively．Vertical distribution of biomass indicated that most biomass was accumulated below middle height of trees．In accordance with the diameter class distribution of biomass，the maximum biomass appeared at trees with 20 cm dbh．This research is useful for broad-leaved forest planting．