Three- dimensional tomography of seismic wave velocity is an important method to study the three- dimensional structure and dynamics of the mantle and crust. In this paper, we study the three- dimensional tomography of seismic wave velocity in northwest China, and show that the lithospheric wave velocity structure in the study area reflecs the tectonic pattern formed by the combination of multiple land- mass amalgamation in the Phanerozoic. These old landmasses include Tarim, Jungar, Qaidam, Turpan—Hami, Yingen, Tengger and Ordos, all of which have high- velocity characteristics in the upper layer of the lithospheric mantle. Three- dimensional tomography also shows that the long- range effects of the India subcontinent’s collision with Eurasia affected the uplift of the Tienshan Mountain, the western Tarim Basin and the Tuha Basin, but the intense deformation formed mainly acted on the upper and middle crust. Based on the characteristics of the combination in the study area and combined with the high- precision data of ground gravity and aeromagnetics, it can also provide accurate positioning of the Phanerozoic dynamical actions the remains, and of the early ocean—continent transition zones.