Subduction is one of the important mechanisms for the formation of the high-pressure (HP)-ultrahigh-pressure (UHP) metamorphic belt. The movement rate and strength of a subducted block are important tectonic constraints on its formation and evolution. Studying the formation process of a HP-UHP metamorphic belt by using plate subduction is a useful attempt to study the formation mechanism of the Sulu HP-UHP metamorphic belt and construction of a dynamic model. The most conspicuous tectonic effect of subduction is strong underthrusting of the land surface at the front of a subducted block and the Moho, which results in the formation of a piedmont depression and accretion and thickening of continental crust. Preliminary numerical modeling suggests that the translational rate of a subducted block is broadly positively correlated with the amount and rate of downwarping of a piedmont depression and the amount and rate of downward flexure of the Moho, indicating that they are boundaries of important intracrustal active tectonics. The migration of the tectonic boundary in the interior of a subducted block, as the movement carrier of deep subduction of a HP-UHP metamorphic belt, indirectly reflects the changes in formation process and movement rate of a HP-UHP metamorphic belt. The results of the numerical modeling seem to show that the land surface and Moho is likely to be boundaries of important active tectonics for the study of the formation process of a HP-UHP metamorphic belt and deep subduction. The tectonic stress field in the interior of a subducted block is also an important tectonic factor for constraining and influencing the formation process of a HP-UHP metamorphic belt. Modeling calculation indicates that the intracrustal stress field of a subducted block during subduction is relatively stable and always dominated by compressional stress, while the strength of subduction only affects the magnitude of stress rather than the distribution of stress in the intracrustal stress field.