The group-VB transition metals vanadium (V) and niobium (Nb) exhibit a simple crystal structure under high pressure, yet display complex physical behaviors, like anomalous compression-induced softening heating-induced hardening (CISHIH) mechanical behavior. This study utilizes machine learning potential molecular dynamics method to investigate the melting behavior and abnormal mechanical softening-hardening behavior of V and Nb under high pressure. In contrast to V, the melting behavior of Nb significantly exceeds current theoretical and experimental results. The shock melting of Nb was first reported. The simulated X-ray Diffraction patterns at high temperatures suggests that the Pnma phase of Nb may not remain stable. Furthermore, the temperature-dependent anomalous elastic properties of V and Nb were investigated within a pressure range of 0-250 GPa. The mechanical properties of V and Nb undergo a transition from HIH to heating-induced softening, elucidating the interplay between thermal-expansion-induced softening and heating-induced hardening. This work based on machine learning potential has further deepened our understanding of the physical properties of V and Nb under high pressure, and has also provided a valuable reference for the study of the high-pressure physical properties of other metals.