Abstract: The development and the structure of the one-year-old and two-year-old root of Scutellaria baicalensis Georgi were studied by paraffin section.The development of root could be divided into four stages,promeristem,primary meristem,primary structure and secondary growth stage.The promeristem is consisted of three groups of initial cells,which have typical cytological characteristics of meristem cells.The primary meristem is composed of calyptrogens,primordial epidermises,periblems and pleromes.Both the calyptrogens and the primordial epidermises initiate from the same layer of initial cells.The primary structure consistes of epidermis,cortex and stele.The primary xylem is diarch.The secondary growth mainly depend on the activities of vascular cambium and cork cambium;the cork cambium originates from pericyclic cells.The structures of the two-year-old tap roots are similar to that of the one-year-old ones,while the periderm thickness is increased.In the secondary xylems of the two-year-old roots,the woody fibers are distributed in groups and the interxylary phellem appears.The vascular rays are multiseriate.Phellem cells surround a sclereid form the phellem cycle in the phloem nearby the periderm.