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As one typical aluminum‐ and sodium‐bearing silicate mineral in the crust, the high‐pressure behaviors of NaAlSi2O6 jadeite are always of interest for investigation. However, the phase transition of jadeite at lower mantle remains elusive; thus, further static compression experiments and systematic theoretical calculations are highly needed. Here, we report a new monoclinic to monoclinic phase transition of jadeite with a volume collapse of 3.17% at around 68 GPa by in situ Raman experiments and first‐principles calculations at high pressures. Such transition leads to the increase of coordination numbers of Si from four‐ to five‐fold coordination, because of Bader charge transfer between Si─O and Al─O bonds. The physical mechanism behind this transition provides important value to understand the minerals in the lower mantle. [ABSTRACT FROM AUTHOR]