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A set of nearly NS-trending rifts developed in the Himalayan orogen and southern Tibet, which are the large-scale extensional structures formed under the continuous compression of the Indo-Eurasia continent, playing a significant role in revealing the post-collisional evolution of the Tibetan Plateau. Different predictions have been made on the spatiotemporal distribution of these rifts through the existing hypothesis models, constituting the key factors constraining the formation system of the rifts. In this study we synthesized previous studies on the initiation time of rifting, and further clarified the spatiotemporal trend. The analysis results showed that the rifting initiated progressively earlier westward, which is consistent with the evolution of post-collisional magmatism in the Lhasa Terrain. Moreover, combined with the geophysical observations, it is inferred that the geodynamic mechanism of the nearly NS-trending rifts accords closely with the hypothesis model concerning the eastward-propagating lateral detachment of the subducted Indian slab. The Indian slab detachment resulted in asynchronous gravitational potential energy gradients, which drove the lithosphere flow eastward and eventually caused the eastward development of the rifting.