In order to build the volume tables for standing trees of natural forests in Vietnam, the authors have conducted research to classify the trunk forms. The date were collected from 84 local species units and 4380 cutting trees in regions: Northern Central Coast, Southern Central Coast, Central Highland. The data analysis results showed that the normal form factor with the bark of species ranges from 0.4563 to 0.5749, while the normal form factor without the bark is from 0.4367 to 0.5349. Basically, the normal form factors of each species is independent to the locality. The normal form factor is classified into five homogeneous groups. Each group corresponds to a volume table unit.