Abstract: On the basis of geological studies of some 28 localities of Ultrahigh-Pressure Metamorphic (UHPM) rocks all over the world it is not difficult to find that most UHPM belts are developed in close relationship with the island arc-continent and the continent-continent collisional orogenic belts. Majority of them are developed within the active continental margins where cold continental materials can be subducted deeply under another relatively stable or non-subducted plate, and the subduction depth of which can exceed 90~120 km. Consequently, under the deep-seated high-pressure (>2.5 Gpa) and high-temperature (c. 600℃ or higher) in combination with other favorable metamorphic conditions the UHP typomorphic minerals，such as coesite and diamond, can be formed. According to present data UHPM rocks are spatially concentrated within Eurasia and at its margins. However, there is still lack of information for North America and Australia. Temporally the UHPM rocks are usually Phaenerozoic in age. The Precambrian UHPM belts are few, only two of them are Neoproterozoic in age (Pan-African stage). It is suggested that the collisional orogenic process with UHP metamorphism be a tectonic regime when accretion of the continental crust reaches considerable thickneses. The statistics of temporal distribution of UHPM belts shows two maxima at Paleozoic and Mesozoic-Cenozoic, respectively. It indicates that the break-up of Rodinia and Pangea caused the lowering of geothermal gradient of the continental crust which is favorable for formation of the UHPM belts.