a-PbO2-type TiO2 (TiO2-II) is an important index mineral for ultrahigh-pressure metamorphism. After the discovery of a natural high-pressure phase of titanium oxide with a-PbO2-structure in omphacite from coesite-bearing eclogite at Shima in the Dabie Mountains, China, a nano-scale (<2 nm) a-PbO2-type TiO2 has been identified through electron diffraction and high-resolution transmission electron microscopy in coesite-bearing jadeite quartzite at Shuanghe in the Dabie Mountains. The crystal structure is orthorhombic with lattice parameters a = 4.58×10?1 nm, b = 5.42×10?1 nm, c = 4.96×10?1 nm and space group Pbcn. The analysis results reveal that rutile {011}R twin interface is a basic structural unit of a-PbO2-type TiO2. Nucleation of a-PbO2-type TiO2 lamellae is caused by the displacement of one half of the titanium cations within the {011}R twin slab. This displacement reduces the Ti-O-Ti distance and is favored by high pressure. The identification of a-PbO2-type TiO2 in coesite-bearing jadeite quartzite from Shuanghe, Dabie Mountains, provides a new and powerful evidence of ultrahigh-pressure metamorphism at 4–7 GPa, 850°C–900°C, and implies a burial of continental crustal rocks to 130–200 kilometers depth or deeper. The a-PbO2-type TiO2 may be a useful indicator of the pressure and temperature in the diamond stability field.