Abstract: [Objective] The arcuate tectonic belt in the northeastern Tibetan Plateau is a unique boundary for the lateral growth of the Tibetan Plateau. Characterized by the arcuate geomorphology with alternating basins and mountains perpendicular to the direction of the plateau's expansion, it represents a unique growth mode of the Tibetan Plateau’s expansion. This study aims to reproduce the the formation and evolution process of the arcuate tectonic belt in the northeastern Tibetan Plateau using the three-dimensional finite element visco-plastic large deformation numerical simulation method, propose a new structural pattern and deformation mechanism for the outward growth of the arcuate tectonic belt. [Methods] Based on a large amount of geological and geophysical data, three tests were conducted to investigate the control of the barrier of Yinchuan Basin and weak lower crust on the development of faults within the arcuate tectonic belt. [Conclusion] The results show that during the process of the Tibetan Plateau expanding northeastward, the shortening and thickening deformation of the crust propagated from the plateau to the northeast. Under the compression of NE-SW, the deep-seated materials in the Mesozoic and Cenozoic basins (arcuate tectonic belts) confined by the blocks migrated northeastward. After being blocked by the rigid Ordos and Alax blocks, they were squeezed into the relatively weak Yinchuan Basin to a limited extent. The obstruction of the Yinchuan Basin is an important condition for the formation and development of the faults in the shallow crust within the arcuate tectonic belt. The weak lower crust promotes the development of faults within the arcuate tectonic belt, but it is not a necessary condition for fault formation. This paper analyzes the distribution characteristics of the maximum shear strain rate on the surface and along three sections of the arcuate tectonic belt and the laws of their evolution over time. It is proposed that the arcuate tectonic belt generally presents a "ramp-thrusting" structural pattern in the deep part, and the deformation mechanism is characterized by deep-shallow decoupling. The deformation of the lithosphere within the arcuate tectonic belt decoupled at the depths of 20 km and 40 km, forming three tectonic layers. The middle-upper crust is dominated by thrust and fold structures, regulating the horizontal shortening and vertical thickening of the crust; the weak lower crust completes the horizontal shortening and vertical thickening of the crust through ductile-plastic deformation, and serves as the detachment layer for the development of arcuate structures; the lithospheric mantle, due to the regulating effect of the Moho surface, underwent a limited shortening and thickening. Under the control of the preexisting fault zones in the south and north margins, the main arcuate faults developed synchronously, then extended to the depth, and finally cut into the middle crust. [Significance] This study deepens the understanding of uplift and lateral growth of the Tibetan Plateau, and provides a reference for the study of the deep-shallow process of arcuate structure formation.