Lithium insertion into anatase was studied by XRD, XPS and ab initio calculations. Lithium insertion in anatase was carried out by n-butyllithium and the product was analyzed by XRD and XPS. A distortion of anatase cell by the lithium insertion and removal was estimated by the ab initio periodic pseudo-potential calculations. As a result, a crystallographic transition from tetragonal to orthorhombic along with a considerable hysteretic change of the cell volume were estimated, which is well consistent with the previously reported XRD cell dimensions. In the lithium-removal process, the wide plateau in calculated cell volume was observed for LixTiO2 where lithium uptake x ranges from 0.25 to I.